@v It did work well before, the last version was so so. Sometimes it tracked fine, sometimes it didn't. On like 0.14 I believe it was working perfectly for me. Misfit seems to tell me that half of my sleep is light sleep and half is deep sleep. I believe this is true since, I don't sleep easily but don't want to wake up in the morning. Anyways, I don't know how Misfit does it but, it works perfectly on their app.
Also, I thought of something. You should add a snooze to the idle alert. So if, I don't start moving 5 minutes after the alert popped up then, it should tell me again. This is just an example. Obviously, it would be off by default but can be turned on in the app settings.