Im using an ELM327 OBD2 sensor with Bluetooth to the torque app to an old $10 android phone and when I cut the key back to EOC it loses power and has a delay to reconnect and sometimes doesn't reconnect at all. A kill switch is the best way. It probably loses power to the ECU and the OBD2 port also.
kill switch should help instead of killing power via the ignition switch. I "think" torque has a setting for using the gps for speed/distance, but the program itself might konk out if you shutdown the adapter, so kill switch.