Just bought this

[RandomHero]

Amazon.com: Soliport ELM 327 Bluetooth OBDII OBD2 Diagnostic Scanner: Automotive


from what i understand to run it on uphone you need a jailbreak, but you can run the Torque app on the android for free!!

 

[RandomHero]

dont have any codes at the moment but it was only $10 shipped. i received it today and plugged it in and just ran the the engine rpm gauge and it worked perfectly, well there was a tiny bit of lag between the actual rpms and the what was reading on my phone. i kinda want a CEL to happen on my car so i can play with it now.

$10 well worth it.

 

[Brains]

You can get a WiFi model to use with your iPhone/iPad and Android. I have one plugged into the OBD-II port on my truck right now. The available free apps are lacking in features and polish (as expected) compared to the pricey ones, but I did find one of the cheap ones that allows you to send raw hex over the port and get the response back. So you can do stuff like '09 02' and get back the vehicle VIN number. I've been kicking around building my own app, but why reinvent the wheel? These things come in really handy at emissions time though, so you know before you bring the vehicle in whether or not all the monitors are in the 'ready' state (OBD-II Mode 5).