http://jalopnik.com/5857359/the-ten-...gets/gallery/1
Came across this on Jalopnik, pretty crazy what you can do now, Gameboy diagnostics? Cobb eat your heart out.
I used Fuelly for a few weeks but lost interest, I don't need a website to tell me my car drinks gas.
I have been looking into iOS monitoring of certain sensors, like oil pressure though.