Well, that could lead you to incubating your dream. Not sure if you are needing this to be lucid or you just wanna get there lucid or not?

Here is a dream incubation tutorial:

http://www.dreamviews.com/general-dr...ml#post1853618

Here is the definition of a lucid dream:

http://www.dreamviews.com/attaining-...cid-dream.html

Waking up every hour and a half(ish) is actually something you have to learn how to do if you want to do without an alarm. With an alarm you probably won't be able to sleep and will have a really hard time remembering dreams.

This will wake you up after like 3 hours or so:
Drink a ton of water before you go to bed! When you wake up after REM, instead of just turning around and going back to sleep, this will make you get up and pee. If you are sleeping longer than 6 hours, you can drink a bunch of water again and you should wake up at six hours. This will wake you up twice.

I have my own way of waking up whenever I want, but that takes about two weeks to a month to get down, don't think it will help tonight.