Got this app 2 days ago and basically what it does is wake you up in your lightest sleep, so you feel AWESOME (instead of like you want to die when you wake up during deep sleep from your alarm clock or whatever).
It is default set to wake you up over 30 minutes. Basically it plays a song (and the songs in the app are incredibly to wake up to, unlike most alarm clocks which just piss you off).
It starts playing the song quietly when you first exit deep sleep and then stops and gets louder each time as you enter lighter and lighter sleep. You can set how loud it goes and also set the time it sleeps for.

This is not necessarily a good app for inducing LD's, which is why I didn't put this in Lucid Aids. But it is definitely a sleep health app and most importantly it is VERY accurate.
I also feel like my sleep is longer. In the morning the last two days I was seriously in disbelief at the amount of sleep I got. I thought I'd overslept yet again (sleep pattern has been horrendous) and I couldn't believe the time when I looked at it. I think because it wakes you up over time, you're semi-aware during sleep and the time feels longer, not exactly sure though, that's a complete guess. But the point is your sleep feels far, far longer than usual and you feel rested.

I guess this could be used for LD's if you want to get woken up, turn the app off and go back to sleep, since you'll enter REM after that. But I think it should be used as a standalone thing, just for sleep quality, as there are other apps for LDing.

After 5 days you get a graph of your sleep and this can help you figure out how you sleep and how to help your sleep get even better (I haven't tested this yet as only been using it for 2 days).

Also to make the alarm sleep, you can just pick your phone up and shake it.
I would also set a regular alarm if you really need to get up at a certain time, but it would be even better to analyse your sleep graph and figure out the best time to go to sleep so the app will wake you up when you need to be woken up.

Also if you get this, don't disregard where it tells you to place the phone, it needs to be where the picture shows you in relation to the person (not necessarily on the edge of the bed as in the picture). It's got a testing feature to help you get the placement correct, it shouldn't go off when you breathe, only when you turn over.

Highly recommend this app 9/10.