I have a Actron unit that is powered by the car and small enough to keep in the car. No laptop required. It allows me the clear the CEL and read the problems. It also works on any car built after 1996.
The only problem I see with this unit is that you have to have your computer with you. I recently needed to clear a code in a parking lot (Chinese food pickup) and was luckey that an oil change place next door let me borrow their hand held unit.
But for $22 (after shipping)? Its your money.
__________________ My Porsche mechanic drives a Saturn. '98 Artic Silver w/ Tip