Today, I spent the day doing some stereo upgrades to my truck.
Need 12VDC and don't plan on needing trailer brakes? Toyota provides a stout, unswitched 12V feed at the trailer brake connector. Details and pinouts are in the manual and the paper in the trailer brake connector package that's included with the truck. The connector is the thing you didn't know what to do with in the glove box.
This feed could be useful for stereo gear, ham radios, and extra inverter, etc...