You have three main options.
Scangauge2 at about 250.00
KiwiMPG at about 90.00 (it's big brother is 299-features comprabale to the SG)
Ecometer by Autometer about 70 bucks.
The Kiwimpg and the ecometer are more basic and tell you mpgs. The SG2 and the KiwiMPG's big brother, the Kiwi have more functions.
Many people here on TN Own and use the SG2, I've read around the nets people seem to like the ecometer as well. I personally have a SG2.
Here is also another thread:
Anyone ever tried the PLX Kiwi? Scangauge?
