[AndrewN]

The relay is classic for this type of application.

If you were using a microcontroller like the PIC in the FRC RC you can do the following:

Connect a loop of wire through one of the "disconnecting" connectors. Call this the docking sensor. Connect it to any input of the PIC.

Connect a start switch through the "disconnecting" connector to a portB input.

Upon reset check the state of the docking sensor. If the input is 0 then you are docked and put the processor into a "low power mode". The PIC processor supports this, the processor is effectively off.

When you close a start switch the processor gets woken by an interrupt that somthing changed on portB, if it was the start switch, wake the reset of the robot/car using a relay/breaker (like a spike relay), if not go back to sleep.

This is really closer to what happens on modern motherboards today.