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Zephyr’s Bluetooth 4 fitness gadget vs. Ant+ (and running nerd ramblings)

Running TechnologyI love combining my passion for tech with working out.  I use bluetooth and Ant+ sensors to record speed, position, heart rate, and cadence.  For years I have used a mixture of devices from Garmin, Zephyr Technology, and various phones.

I like Zephyr Technology. They make cool bio-metric technology. I bought their original HxM bluetooth heart rate monitor strap years ago.  At one point their marketing guy sent out an email to customers asking for feedback. I griped about my one complaint with the product, that they charged extra for access to the SDK. I told them it was silly to make developers pay extra for the privilege of helping them sell more product. It’s not like their SDK could benefit their competition, it was just a message structure API.  I don’t know if I deserve any credit but it appears they actually changed their policy and now prominently give open access to their SDK.  Two thumbs up for open API’s.

A few months later I got a generous offer from their marketing guy to review new Bluetooth 4 (aka “Bluetooth low energy, BLE, or Bluetooth Smart“) heart rate strap.  So since I love testing gear, I love fitness gadgets, and I love tech, I jumped at the chance.

So the quick summary: It works well with my MotoActv fitness watch. I ran with three heart rate monitors. I had the original HxM connected via plain bluetooth (spp) to my Samsung Galaxy Note using the “Runtastic” app. I also had a Garmin Ant+ heart rate strap connected to a buddy’s borrowed MotoActv and the new Zephyr BT4 monitor connected to my Motoactv. The result: The two MotoActv’s were nearly identical in measured heart rate. Minimum, maximum, and average were within a single bpm of each other and the minor variation very well could be due to not pressing stop and start at exactly the same time.

Clean smooth data from the new Zephyr
Clean smooth data from the new Zephyr

The original HxM data was significantly different. It was a much lower average and it was not nearly as steady a heart rate as the two MotoActv’s indicated. But it is hard to condemn the HxM without further testing. I did have quite a bit of bluetooth traffic, I had the headphones streaming music from the MotoActv while also maintaining a bluetooth hands free link with my phone. And the Broadcom bluetooth chipset in the Samsung Galaxy series is notoriously problematic in Android. Several app developers have specific hacks and workarounds to deal with the flakiness of the Broadcom bluetooth in Samsung hardware. So the HxM data was definitely skewed too low. I’m in pretty good shape but not good enough to 5+ miles at sub 8 minute miles with a 110 average heart rate. But it will be another article to nail down the source of the error.

Runtastic App Screenshot
Captured with Runtastic App on an Android Samsung Galaxy Note. I think the data issues might be caused by the strap.

The comfort of the new strap is subjective. I find the new Zephyr more comfortable than the Garmin Ant+ because almost half the Garmin is slick, non-stretching plastic. A greater portion of the circumference of the Zephyr is elastic material. Greater amount of elastic + lesser slick surface = less slippage (or less tension to avoid slippage). That said, I think the original HxM strap is superior to the new strap. It appears to use conductive thread so even the electrode contacts are puffy and made of fabric. The new strap is one continuous elastic band with polymer pads for electrode contact. Where the polymer makes skin contact, it is not as pleasant as the old strap. But the new is probably more durable and probably gives better performance.

So it works, it gives identical data to my Ant+ strap, its comfortable, and it solves the annoying need for that weird charging cradle of the HxM because it runs off a coin cell. I only got to test it with my MotoActv. It should work with the iPhone 4S, iPhone 5, and a few of the newer Motorola Androids. I don’t have any other BT 4 straps to compare it against but it seems to be a good option.

So I keep up on fitness technology and plus we have a project under development that might have a business case for Ant+ sensors. So I learned a few things testing this strap that might be of interest to running gadget nerds (both of us):

The MotoActv is capable of connecting to both Ant+ devices and Bluetooth 4 devices but not both at the same time. So if you connect the new Zephyr strap to the MotoActv, I can’t use my Ant+ foot pod at the same time. Note that streaming bluetooth music from the motoactv is totally independent of this limitation. You can stream bluetooth music over A2DP headphones while connected to Ant+ or Bluetooth 4 fitness sensors. Since as far as I can tell, there are no bluetooth 4 pedometers, that’s a definite point in Ant’s favor. It does appear that there Bluetooth 4 bicycle power meters so that is a tie on that point. I’m guessing this has to do with the fact that Ant+ and BT4 operate over the same frequency and thus probably share a single antenna in the MotoActv or it might be due to BT / Ant sharing a single chip and antenna on the Motoactv.

So I learned something else interesting about the difference between BT4 and Ant+ protocols that could be a bug or a feature for either protocol depending on your needs. Ant+ data from a single source can be received and decoded by multiple receivers. Bluetooth 4 appears to enforce a one to one relationship. When I wore my Ant+ heart rate strap, I could read identical data simultaneously on my MotoActv and my Galaxy Note with an Ant+ adapter attached. When I wore the BT4 strap from Zephyr, I could only read data on one whichever motoactv connected first. I don’t know if this is encryption or handshake based. But I can see pros and cons to both approaches. With Ant+’s multi-receiver mode, you could have a team of runners or cyclists simultaneously be able to see their own data and be monitored by a coach. I even saw an application in the Android market that would let you listen to all the Ant+ power monitors in your riding group and show who was pulling the hardest. But I can also see the value of data privacy. I doubt Ant+ could ever go private, that would require complexity probably not present in the transmitter. It might be possible BT4 could allow multi-receiver in the protocol, not sure.

The interesting thing to me is how full circle things have come and how Apple’s iPhone business model makes good capitalism but I find a little unfriendly to tinkerers and hobbyists. The original Zephyr HxM was the reason I switched from iPhone 3GS to Motorola Atrix a year or two back. Apple refused to allow developers to connect to bluetooth SPP (serial port profile) devices even though the hardware and software were fully capable. There were a few exceptions of big name companies that paid high fees and got their application certified. Apple demanded an iron grip on the user experience and refused to give the developers the freedom to make innovative but potentially battery draining (and potentially buggy) software. So I jumped ship to Android and have enjoyed the freedom to hack immensely. I’ve even got my phone hooked up to my car’s OBDII adapter via bluetooth SPP:).

But now that fitness and health gadgets are a small but growing market, the Bluetooth SIG decided they needed to compete with Ant+. And even though I think Ant+ is superior in several ways, Bluetooth 4 has some mighty big coat tails to ride since bluetooth is in almost every phone on the planet. But the surprising thing to me is Apple’s IOS fully supports Bluetooth 4 for the last two hardware cycles (4S and 5) while Android lacks even an official Bluetooth 4 API! The latest (as of late 2012) Nexus 7 tablet from Google has a Bluetooth 4 capable chipset but there is no API to access the hardware. Motorola has their own BT4 API but it is quite frustrating to see the “walled garden” IOS ecosystem be so far ahead of Android. Android is supposed to be the OS of freedom and choice.

Note: There is a follow-on to this blog post, which can be found here.

8 Responses

  1. Great read. I’m curious as to where to find this exact device your using. I notice the only smart bluetooth devices are made for iphones only…are you using the iphone version and pairing it to an android phone? Anyway…thank for the intelligence. Certainty its a brave new world for hrms with lot of challenges, I appreciate the heads up.

    1. I have not tested on an iPhone at all, but I have no doubts the technology would work. All my testing has been on Android phones and the Motorola “MotoActv” fitness watch (which is really an android device under the hood, just not a phone). Here are some links for you:
      The original HxM is compatible with any device that supports the older Bluetooth 2.1 standard except the the iPhone. It does require someone to write custom software to acquire and display the software so even if a device is technically compatible, it may or may not have sofware. But as far as I know it will support just about any Android or Windows phone and at least a few Symbian devices. It can be found here
      The latest version of Bluetooth, bluetooth 4, is a little different. Zephyr makes a Bluetooth 4 HRM here. It is compatible with all the apple products since the 4S. It has better battery life and is easier to write software for than the one above. A few Android devices support it but it is not yet officially supported in the core Android operating system (but I would expect that to change very soon, like maybe announced in the next few days at Google I/O).

      The Ant+ HRM monitor I used I got with a Garmin GPS watch but they sell them separately on their web site.

      The MotoActv is available off the shelf at Best Buy, REI, and online.

      I would hold off a couple weeks buying anything until we see what is announced at the big Google conference in the middle of May 2013. I would expect some products and software to be announced that might change your mind or maybe change the prices.

  2. FYI, the multi device linking is part of Ant+ and *not* part of Bluetooth….can’t be changed since it’s part of the specs for each.

    Main problem with Ant+ is only some phones have the hardware and the Samsung ones don’t 🙁

    Android 5.0 in October will finally support BTLE.

  3. Forgot to mention that the other main difference between the HxM and the HxmSmart is that the new one doesn’t have the cadence motion sensor. It matters less for running because we have GPS nowadays, but if you use it to monitor you during tennis like I do, the old one works better…

  4. A little late to the discussion but…
    If I buy an Ant+ strap such as from Polar or Garmin, AND I buy an Ant+ adapter for my 4S with Endomondo app installed, can I simultaneously monitor HR on both devices? That would be awesome.

  5. Very helpful blog! Maybe you can answer my question?
    Is it possible to use Ant+ sensors with apps that are designed for Bluetooth sensors? Actually I’d like to use the Garmin HRM with SportsTracker. I have a Galaxy S6 which supports with Ant+ and BTLE. I found apps that can read the Ant+ data but is it possible to make the Ant+ Sensor emulate a Bluetooth sensor so it feeds its data to SportsTracker?
    Thanks kindly,

    1. Sort of but not easily. Can an Ant+ device talk directly to an app that was written for Bluetooth low energy? No. But there are translator devices that can capture data on one protocol and then rebroadcast on BLE. Specifically Viiiva Ant+ to BLE bridge review on DC Rainmaker. But for what I think you are asking, the answer is no. An application designed to talk to a Bluetooth sensor cannot be tricked into receiving Ant directly. I’m planning on another article about bluetooth vs. Ant so check back in a couple weeks.

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