Good Morning Alarm Clock is a very special alarm clock app, because it actually gives up something that might be considered essential for its type, punctuality, in favor of a better sleep. What does that even mean? It's simple: when you sleep you go through different stages of lighter and heavier sleep. A key to feeling well-rested is waking up during a light sleep stage, and that's what Good Morning Alarm Clock tries to achieve, although that might mean waking up 20 minutes before or after what you expect. In fact, when you choose the alarm time, you should always think of it as an approximate time.
To use Good Morning Alarm Clock correctly, you have to place your Android device under your pillow, so it can use the accelerometer to check if you are going through a light or heavy sleep phase by how much you're moving in bed.
It's hard to tell if Good Morning Alarm Clock is really effective, but on paper the idea sounds great. That said, the fact that it's not punctual might make it problematic for daily use.