I also suffer from the only can sleep about 4 hours at a stretch syndrome. If by chance I don't wake up, then my big ol' dog wakes me up by starting to fuss; if the fussing doesn't work, he'll lick me a couple of times and if even that doesn't work he'll step right in the middle of me to get off the bed. He sleeps on the other side of the bed, all stretched out like a person does, with his head on the pillow. Can he get off the bed on his own side? No, of course not.
I don't have to worry about taking him outside to pee, because he has a doggie door and comes and goes as he pleases, but if he steps right in the middle of me (he's 70+ pounds) it is a very effective wake-up call.