I have an I phone4 and am running DashCommand from the Itunes App store. I`m using a WiFi dongle (part that plugs into the OBDII port). it works as asvertised and gives quite a bit of info. it even gives you 0-60. 1/4 mile and G forces! you can read and erase codes if need be. on Fords, you do have to purchase an extra app to read data from a particular year, it is an extra $10. so for me it cost me a total of I think $20 for the app and an extra $10 for the extended app (2002 Ford) and 15 for the WiFi dongle! well worth it.
The main reason I bought it was so I could watch my trans temp, however with all the info. it gives I have the gauges setup so I can watch my trans temp and engine temp off the same gauge. and the gauges can be configured any way you like.