I think the AEM is the best bang for the buck. $500 includes harness and G meter. Sensors extra, but still way cheaper then a Racepack.

I have the innovative ssi-4 in my car with a AEM wide band gauge. It was only $129 new, but requires the laptop in the car to data log. For as cheap as it is, it's worth leaving the laptop on the front seat in my opinion.