Continuous Heart Rate Variability Recording for $70

Heart rate is an interesting signal when you’re working out, and it’s sort of interesting indicator of cardiovascular health when you’re resting. But if you look at the variation in the intervals between heartbeats (HRV: heart rate variability), then you get a good indicator of emotional arousal, stress, breathing rate, and even sleep quality.

So, if I want to continually measure my HRV all day, especially while I’m working at my computer, what do I do? Complain about how inconvenient it is for a year, and then hear from Randy at BodyTrack / Fluxtream about the Polar H7, which can send RR intervals using Bluetooth Low Energy for days at a time on a charge. A day later: he’s written a Mac app to connect to the strap and send the data to BodyTrack / Fluxtream. A day after that: I’ve ported that app to iOS. If you have an iPhone 4S or 5, an iPad 3, or a 5th gen iPod touch, then you can pick up a Polar H7 and some extra batteries, email me ( Randy to see about getting a copy of the app, or just check GitHub for the code, and have HRV data forever. I’m shocked at how easy the new Bluetooth protocol makes pairing. You never have to think about it.

And, since the data is on Fluxtream, you can easily compare the data–to the second–with any other data streams you want to hook up, like FitBit, Zeo, BodyMedia, Withings, Google Latitude, Quantified Mind, Flickr, Picasa, Twitter, Mymee,, Github, or any custom connector you want to hook up to their API. I can see, for example, how different songs affect my emotional arousal, or how stressed out I am depending on my location. Nice.

6 Responses to Continuous Heart Rate Variability Recording for $70
  1. Caroline Meeks
    February 19, 2013 | 10:36 am

    How did this go? Did you find out anything interesting? Did your code work well?

    I’d like to try it if you had good results.

    • Nick
      February 20, 2013 | 11:43 am

      I haven’t been working on this lately, but Randy made some improvements, and I’ve sent a bunch of readers his way who have gone on to test the app. I’ll update the blog post to let people know to contact Randy directly, as I’m a bit out of the loop now.

  2. Rory
    March 19, 2013 | 10:53 am

    Would you be willing to share your iOS code to extract the RR interval data?

  3. Nick
    March 19, 2013 | 11:22 am

    Sure–email and I’ll send the code over, or email Randy (address given in the post) to see about being added to the TestFlight distribution for testing the app.

  4. Simon B.
    October 6, 2013 | 6:31 pm

    Hey, how are things going with the app?

    • Nick
      October 6, 2013 | 7:03 pm

      Randy’s been taking care of it, so if you’re interested, try dropping him an email.