This is not exactly the same, but the app called 'Kaloer Clock' has many different settings and even one that will automatically put your phone into Airplane Mode when your alarm is set. I imagine that the only reason you want to turn your phone off is to avoid disturbances from emails, notifications, phone calls or texts during the night. If that is in fact what you are looking for, then this app should provide that functionality. (or like previously mentioned...simply putting your phone in Airplane Mode manually.)