From what I've read through research....the iPhone doesn't work well or at all with the bluetooth OBD II connection. I may be wrong. I bought the PLX Kiwi WiFi and linked it with my iPhone with the DashCommand App. If I use the supplied "dashboard", it seems to work fine with no lag, but if I try to use other dashboards that I download, it seems to lag a lot with my iPhone 3GS and my newer iPad.
If I had to do it again, I'd go bluetooth and use a Google Nexus 7 tablet or something with Android. My iPhone is too small and my iPad is too big for mounting
I would've waited to get the iPad Mini if I knew it was coming out :P