I found this on the blog lifehacker: A comment by one of their readers that Salvador Dali used to take naps by first imaging holding a spoon in his hand and then falling asleep. It would take about 20 minutes for the imaginary spoon to "fall" and the "sound" of the spoon falling would wake him up. Hmm.
If that doesn't work for you (I'm not sure my imagination is that strong), try these other nap tips:
Tips for Great Naps
If that doesn't work for you (I'm not sure my imagination is that strong), try these other nap tips:
Tips for Great Naps
I think you need to re-read the Lifehacker post. They use a REAL spoon and the REAL spoon falls and makes REAL sounds to wake you up.