Top positive review
If yours doesn't work, read this.
Reviewed in the United States on May 15, 2017
It's easy to use, not very large, has good range (about 15 feet for me), and works very well.
I found that this one didn't initially function at all. No lights, no detection. After a little online digging, I found that sometimes these get confused before the initial use and won't start up the first time. The solution is to put the battery in backwards for a good ten-count and then put it back in correctly. The reason this works is that electrically, it shorts out the battery contacts without shorting out the battery (it's perfectly safe). Or, in effect, it "cold boots" the device. While I was initially frustrated and angry that it didn't work out of the package, knowing that it can be reset if there is an error increases my confidence in the product.
This is actually my second unit. The first one got lost and never failed or required a battery change in the couple of years that I had been using it.
I've had no problems with it being detected by my Android (Samsung) phone, and it works immediately with the phone and laptop applications that I use it for (Zwift and Strava).