It's just that I depend on the current behavior, which is different between home and car.

Edit: More detail:

At home, people need to be able to connect to the shell to do certain commands, or the player needs to be able to hear the "please reboot" command so that it can get a new logo or a new kernel from Logoedit. Yet, in order for GPSapp to work, the player must NOT be listening to serial.

If you make it one-bit, then I have to manually switch each time I move between home and car.