I installed this:
http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WD1V
It's a wireless relay set up. I run power from (ALWAY ON) +12v from the car battery, then connect it to the Power and Reset buttons (I have an opus 150, so I just spliced in a couple more power lines to the existing power wires.
Now I can power on and off and reset my computer remotely. It works about 10 ft from the car, maybe more. For a case, I just got a nice travel soap dish from Wal-Mart ($1) made of plastic (so it won't interfear with the RF signal) and drilled a hole in the side.
Works like a champ and it's very portable.