Review: Mobility Rev Bluetooth Heart Rate Monitor

I recently discovered the PCD Mobility Rev Bluetooth HRM on Amazon.com, for the ridiculously low price of $7.95 including shipping (currently also available on eBay for $9.95). This is a Bluetooth 4.0 (Bluetooth Smart/Bluetooth Low Energy) HRM with strap, for half the price of a replacement strap for a Garmin or Polar HRM! Despite the 1 star reviews on Amazon, I figured that if the HRM was total trash, I would still have a decent spare HRM strap. It arrived a few days ago, and I put it through its paces on a couple of workouts. I wasn’t expecting much, given the bad reviews, and was pleasantly surprised to find that it’s actually a decent piece of hardware.

Specifications

  • strap length: 70-120cm
  • battery life: 1800 hrs (5 yrs x 1 hr/day)
  • battery: CR2032
  • range: ~10 meters
  • waterproof: IPX7
  • operating temperature: -10C – 50C
  • weight: 47g (transmitter+strap)
  • SKU: LHX0021Q

The company seems to be out of business, as their website is dead: http://www.pcdphones.com

The receiver is a bit chunkier and clunky looking compared to my Garmin HRM:

hrmfront

Note how it uses industry standard metal snaps, spaced that the standard distance, so the receiver and strap are compatible with Garmin/Polar/Wahoo/etc.

hrmback

The Mobility Rev uses a CR2032 battery (included). The battery door has a rubber o-ring to seal out moisture from your sweaty chest. I don’t know how water resistant it is, however, and am not going to try immersing it. Unlike the Garmin, which requires a small Philips screwdriver to replace the battery, the Mobility Rev’s battery cover easily comes off with a twist of a coin.

The Mobility Rev strap (bottom) is the same quality and of similar design to my Polar strap (top):

hrmstrapfronthrmstrapback

I use the Polar strap with my Garmin HRM, because the fancy strap that it came with has rather sharp and hard edges that chafe during a long workout.

So far, I have taken the Mobility Rev HRM out for a 1.5 hour bike ride and a 3.5 mi trail run, using the Wahoo Fitness app on an iPhone 6, and it has worked quite well. Here are the metrics I use for evaluating wireless heart rate monitors:

  1. accuracy: Since this is a cheapo HRM, I’m not going to do detailed testing with graphs. At steady state, the heart rate reading is identical to that from my fingertip SpO2 meter. On my 1.5 hour bike ride, I didn’t bother to bring another HRM to compare against, but the heart rate readings looked consistent with my experience, and there were no dropouts or spikes, even when I was riding over very bumpy pavement. On my 3.5 mi trail run, I brought along my Garmin HRM, and did concurrent recordings. I was disappointed to find that during the first minute of recording, the Mobility Rev spiked up abnormally to 144 bpm before stabilizing at my true HR of 109 bpm. This phenomenon, however, is a regular occurrence with my optical HRM’s (Wahoo Rhythm+ and Garmin Forerunner 225 built-in). Since I was wearing two heart rate straps, making the sensor placement less than ideal, it’s possible that this glitch was due to poor contact with my chest. After this initial spike, it settled down, and had identical readings to the Garmin during the rest of the workout, deviating by 1 bpm on occasion, even when my heart rate was fluctuating, due to my switching back and forth between hiking and running. My Pyle strap often spikes up to unrealistically high HR’s when there is intense vibration from my running. The Mobility Rev displayed no such aberrant behavior. For the most part, I was impressed by the accuracy and consistency of its readings.
  2. signal stability: During use, the signal was rock solid and never dropped out.
  3. range: my iPhone 6 was able to reliably receive the signal 40 feet away from the HRM even while indoors.
  4. overall fit and finish: The plastic casing seems of decent quality, and the strap is of comparable quality to the Polar HRM strap.
  5. reliability: Since I have only had it for a day, I don’t yet know if it will crap out after just a few uses. I will update this article after more testing.

Using the free LightBlue Explorer iOS app, I found that it identifies itself as BLUETOOTH SMART HRM, and reports the following device information:

bthrminfo

The manufacturer string is Maxwell Guider. It’s a nice touch that it seems to support reporting of battery status, but I don’t have any partially dead batteries to test with, so I don’t know if it actually outputs anything besides 100% [Update: see below, it always outputs 100% even with bad batteries].

One caveat of the Mobility Rev HRM is that it only outputs heart rate, so you can’t use it for HRV analysis, which requires R-R interval data. I tried to use it with the Elite HRV app on my iPhone, and it wasn’t able to read any HRV data. As a cross check, I took a look at the raw heart rate data output, and found that it indeed only reports 8-bit heart rate and nothing else.  Most people, however, are only interested in heart rate, and won’t find this to be a problem.

I have only had the Mobility Rev BT HRM for a day, so I don’t yet know if it will stop working after only a short period of use. If there are any changes to its performance, I will update this article. Even if it does fail, I’ll still be happy to have an extra $8 Garmin/Polar/Wahoo/etc compatible strap.

Update 2015-11-24: After only 3 days of use, it died. I tried putting several new CR2032’s into it, and it was still dead. I was ready to write it off as a piece of junk until I finally found one that works. Now, it’s working perfectly again. I think the people who are reporting on Amazon that it connects inconsistently or fails after a couple of days are just suffering from weak cells. This device seems to need a higher voltage than others in order to function properly. The functional cell has an open circuit voltage of 3.25V, while another that reads 3.21V doesn’t work. This makes me question the manufacturer’s claim of 1800hrs battery life. Also, during this testing, I found that the Battery Level service is fake, and always outputs 100%. Some of the weak cells would actually operate it for a few seconds at at time before cutting out, and it still outputted a Battery Level of 100%.

 

Update 2015-12-03: I’ve used the Mobility Rev HRM for at least 8 hours of cycling and running workouts now, and the readings have been absolutely rock solid. No spiking up of HR during the start of a workout, no spiking up of HR during running, and no dropouts. The HR readings are totally glitch free. One problem I’ve had, however, is that sometimes, it’s a bit difficult to get the unit to wake up. I wetting the strap contacts usually helps. One time, I had it mounted upside down on the strap, and it woke up when I inverted it. I’m surprised that it seems to be sensitive to L/R, but unit is actually labeled for left & right sides on the back. In the meantime, the price dropped to $6 on Amazon, so I ordered a 2nd one to keep as a spare.

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