I looked at getting ones of these a few months back scan gauge 2. my mate with a VX turbo bought one i have currently got it and it works fine. Not sure how good the ECU fault scan is i scanned my car and it came up with no faults but i think i may have a small issue with my EGR valve.
But yes it gives you mpg, top speed, temp all sorts.
It is good but i used it once then its been sat waiting to give it him back. Matt if you want to have a look before i take it back send us a PM.