I have an app called "Android Sleep" and it monitors your movement in sleep to determine your sleep cycles. you can also set an alarm for a certain time and it will wake you up RIGHT before a REM cycle

Although it's only a 2-week free trial, I think it would be worth it to buy the whole thing if it will wake you up in REM sleep every time you set the alarm (it's made to wake you up before a REM cycle so you can go to work or school more refreshed).