So it seems Apple recommends an adhoc wifi network to connect the iphone/ipad to the OBD device.
Why don't you support USB or Bluetooth OBD-II interface hardware?
We have investigated the new hardware integration features of iPhone OS 3.0, which in theory allows us to support Bluetooth and Dock connector-based hardware. However, after confidential discussions with Apple, we have concluded that WiFi is still the most reasonable option at this moment—both from technical and business perspectives.
We will not be supporting Bluetooth or Dock Connector OBD II connections yet—but we continue to persue this option and will announce any updates as soon as we have them.