Been there, done that. Actually tuning your car and making it faster over OBD-II? That's genuinely new, and that's what SCT is up to with its iTSX. For $350 you get the Bluetooth dongle and access to a free app that works on iOS devices. From there you get access to limited tuning parameters, like specifying idle RPM and fuel type. If you're familiar with SCT you know that's probably a little limited, but if you go to an SCT-authorized tuner they can create custom tunes, tweaking way more parameters than that, and download those tunes to your device. You can then apply them whenever you like or, even restore your stock tune if you're feeling really crazy. Compatibility is a little limited, though, only working with Ford and GM vehicles '96 and nearer. Right now the hardware is ready, just waiting on App Store approval, so look for release in the coming months.