A million-[insert currency] idea: For free!

[Suicide Junkie]

I like it!
Lower power usage also means less heat in your lap.

I had my old thinkpad laptop hooked up to a power meter a while ago, and I noted (at 12v I think maybe)

0.7 A idling (idle CPU, Memory, power conversion losses, video/audio cards, etc)
an extra 0.1 to 0.2 A when the CPU was going.
0.3-0.5 A for the LCD & backlight, depending on brightness setting.
About 0.5 A for HDD and/or CD activity. Plus a spike when they first spin up.

If you got a dedicated wireless circuit to blindly feed data back and forth sorta like a beefed-up wireless mouse, it would probably sip the juice, and the back light could be your biggest drain.