Actually, would be kind of neat to also install an electric actuator for the driver's door that was controlled by a remote. You could then set it up like a "modern" keyless entry. One button push would trigger the electric actuator and open the driver's door. A different button, or a double click on the main button, and the solenoid would kick in and unlock the rest of the doors. Locking, hopefully you could make it so one button push triggered both the electric actuator and the solenoid to lock everything.
Anyway, that's one idea. Go forth and make a DIY guide for the rest of us!