I use beeminder to hold myself to a 1am bedtime (my graph is here). I don't use any fancy inputs, I just type the time I'm going to bed in on the app just before I get into bed.

It does give me flexibility to sometimes be up late, as long as I've gotten enough buffer ahead of time.

It was easiest for me to set the input format by entering time in a 24 hr format, where noon is 0. Thus, my bedtime of 1am is 13, and it's easy for me to indicate a midnight (12) or too late 2am (14) time without having to do math on how many hours past bedtime I am/use negative numbers.