Yesterday, in his New York Times column, David Pogue reviewed the Zeo, a sleep analysis tool (you may need to register to read it). You strap on a headband and it can show you your waking, REM, light sleep, and deep sleep periods. If you have trouble sleeping this thing will tell you that, yep, you have trouble sleeping.
But we're all after efficiency. A great feature of the thing is that you can set your alarm to wake you when you are in light sleep, so you don't wake up groggy. It won't wake you later than a predetermined time. And, over time, I suppose you could start seeing whether your sleep cycles are 90 minutes or something else, so you can plan to go to sleep so a light sleep period coincides with when you should wake up. And you can see how that works for naps.
I've always wanted a nap alarm that I could set, not for 20 minutes, but to go off after I had been asleep 20 minutes, which is quite different.
The thing costs $400, so I'm not getting one any time soon. But there will be competitors and cheaper, more effective versions coming along. Then I can finally get into sleep training.