I've been beta testing the WakeMate for a couple months.

The battery lasts about 2 nights, and knowing this, I recharge it every night. Since doing so, it hasn't run out of batteries during the night.

The app crashed a lot initially (I'm on Android), but that was months back and the WakeMate guys were good about using the feedback data I sent to fix the bugs. It hasn't crashed for me in weeks, since I installed their latest version.

Edit: I meant I recharge the wristband every other night, not every night.