[BoppreH]

I also had alarm clock problems in uni. My solution was a Raspberry Pi, a piezoelectric buzzer, and an ultrasonic distance sensor pointed at the bed.

The buzzer would ring until the distance sensor could see the opposite wall, and restart if I went back to bed. As a bonus, it took a few measurements during the night to track sleep quality.

Unfortunately the whole thing was running from a finicky breadboard and needed frequent calibration.