If you want the optimal wake feature to work you need to leave the app running. If you just want to collect data and wake up at a predetermined time you can background the app. Unfortunately this is a limitation imposed by iOS.
I can't answer for the original poster, but for me...
At night is when I charge my phone and there isn't always a plug near where I sleep.
Having my phone have to run at night without a charge will mean it's not fully charged at the beginning of the day, which is a very big deal breaker for me. My phone will last the entire day, but only if it's fully charged when I get up in the morning.
As a person who pre-ordered the phone, that is appreciated very much:)
So with Wakemate, if it could run in the background with no need to be plugged in and screen shut down , relying on notification, that would be a great improvement.
I wanted to chime in on this. I may not use my phone at night, but it is certainly receiving notifications and SMS messages throughout the night. This means that with any iPhone alarm, I have to go through numerous close dialogs just to get to my alarm in order to turn it off. A minor annoyance, but the wrist band helps. Otherwise, I'd have to go through my settings and disable notifications prior to going to sleep so as not to disturb me. <-- Heavy sleeper