Try tapping your forehead with forefinger while counting up to the time you want to wake up just before you close your eyes to go to sleep..
eg to wake at 6am...
tap six times while saying "1, 2, 3, 4, 5, 6"
Repeat 2 times, (3 times in total)
Emotional freedom technique (EFT)?
Seems it is for relieving emotional stress but i had only used it specifically to wake up at a specific time.
In EFT you're tapping on the end points of the meridian lines to send a kind of "reset pulse" to clear emotional issues. (At least that's the concept.)
To set a "wake up call" you (basicplus2) tap your head with your finger, but probably not on a meridian point, and you're not trying to clear an emotional issue. Also, some people tap their whole head on their pillow instead.