Originally Posted by mach4

No I don't plan on leaving the key in all the time. I've got a supplemental set of gauges that run using a bluetooth connection between a microcontroller mounted in the engine compartment and an old Android phone. The connection can be finicky when reconnecting, so every time I shut the engine down the gauges may not reconnect reliably. Once it's connected it's bulletproof. I'd like to be able to leave the ignition on during short stops to keep the gauges active. Don't want to leave the microcontroller on all the time and risk running the battery down.

Engine Instrumentation Project