You might want to consider a charge pump.
It is a signal that is given out by the controller when it is ready to go. They come included on some BOB's.
I recently bought a C1G from CNC4PC and it has an enable function. It needs 5 VDC to run the BOB and without the BOB powered up, it sends no signals. So effectively there is a charge pump switch to turn on the BOB and enable the controller. It is better than not having anything.