A power trunk lock solenoid installed where there was none before. It slipped right on, and bolted right down. All I need to do is run a wire to a switch inside the car.

Ok, so.. Long story short, our Canadian Tire had a $30 Eliminator 1.8W solar panel on sale for $10 this week.

Here's my "partially-assembled-and-disassembled-for-the-photo" breadboard power supply. It comes as a kit from SparkFun Electronics