So glad I stumbled on this thread. I think this technique is definitely worth a try, so I just purchased an Invisible Clock II...which seems to have all the bells and whistles I need to experiment with either sleep interruption OR signaling myself to do a reality check at times I KNOW I will be in REM sleep. I have only had two meaningful lucid dreams so far, but thanks to a well-placed digital clock I know the exact times I woke from each, and they were within TWO MINUTES of each other. I'm going to use the Invisible Clock II to vibrate at about 4:08am as I've awoken from my LD's at 4:18am and 4:16am respectively. I should have it in-hand mid-october - a week from now.

DH