It won't have a key, but we offer a remote latching solenoid that utilizes a small momentary on/off button to latch and unlatch the solenoid for battery connection.
You can hide the switch and just have a simple button to hit when leaving the car.
http://www.painlessperformance.com/webcat/30206
A few other options as well:
http://www.painlessperformance.com/webcatalog/badi