[Sean.Heihn]

To be able to measure ECU sensor data, you'll need some sort of OBD2 adapter, Bluetooth are the most convenient but USB to OBD2 adapters will work if your phone is USB OTG capable. Otherwise, you'll only be able to read the phone's onboard sensor data, like GPS, gyroscope, accelerometer, etc...

Also, a gyroscope will be more accurate than the fluid filled inclometers in respects to false readings. And it wouldn't be hard for an app to differentiate between acceleration/deceleration body tilt and incline by using accelerometer data. I.e. braking would produce a different accelerometer reading than going down hill, yet both would cause the body to tilt forward.