system
A chat on subreddit /r/me_irl
human
Grab your keys/keychain,lay down,keep your hand with the keys hanging above the ground.

Your hand will relax and drop the keys(your alarm) about 10-20 min after you fall asleep.
gpt
I'd 100% put my hand against my face and take an eye out or something.

Edit: which I realize is a pretty effective alarm clock as well