quick and dirty code reader and erase function, Costco, 35 bucks.
Self powered, plugs in the OBDII port. To have around for quick and easy stuff, 35 bucks is nothing.
http://www.codekeyunlock.com/what.asp
I got one the other day to zap a couple O2 and HO2 sensor codes in the wifes Vulva to see if they came back. Reads fine on the BMW's too, so I would say it is probably a good all around device.