Product review (2 stars): 1st unit worked for only 14 days, 2nd unit died after 17 days
The first unit seemed fine for two weeks, aside from the fact that the app has no option to update the readings from the device (day old readings are not of interest to me.)  I found the only way to get an update was to close and re-open the app 3 times.

Then on day 15 it stopped responding, completely. I sent a support request via the app. I got a response the next day. The support rep had a free replacement unit sent to me. It arrived 8 days later.  The 2nd unit stopped working after 17 days. (No drops or other mistreatment.)  Both units are completely unresponsive even with freshly purchased batteries, they don't even blink when the battery inserted. Reading other reviews, I see that this experience is not all that uncommon.

I gave it two stars, instead of only one star, because the two support people that I interacted with (via the app and via email) are trying really hard to do their best to help, but they're dealing with a product that is a poorly executed attempt at a fantastic idea.  Dead hardware is dead hardware, there's nothing anyone can do by phone or text to revive dead hardware, but they are trying hard to help people with these devices