I would personally stick with the "PLX Devices Kiwi Bluetooth" OBDII adapter, and download the Torque applications to run alongside it (there are several Torque apps - some cost a couple bucks, some are free). I use these with my Droid2, and they're fantastic. Not only does it read/clear codes, with a touch of a button, it will automatically take you to an online database that gives you a TON of information on what the code really means, what is probably wrong, and how to fix it. Furthermore, it does all the stuff that a G-Tech device would do (horsepower calc, 1/4 mile times, 0-60, 0-100, etc.), and can also serve as a really accurate lap timer (via the GPS tracking and mapping system). Another nice thing is you can be messing with your engine and have the Droid with you to look at all the data while you're doing the work - it connects via Bluetooth, so no wires to get caught on anything (I can be anywhere around the car and never lose the signal). This alone made the unit pay for itself - I had an O2 sensor fault on my JGC, and I set the app up to read and graph all the O2 sensor voltages in real time. One of them was really erratic, and looked like a bad connection or possibly a bad sensor, so I went around jiggling the wires/connectors until the voltages followed the right waveform - found the busted wire really easily. For $100 for the PLX Device, and $5 for the Torque app, you just can't go wrong.