Our laptop works well when powered from 12V. Similarly, cell phones, camera battery charger, mp3 players, etc. I still do not find the need to have large voltage inverter to power 110V devices, but I must admit that there is always a need for more 12V power outlets in the car.
I decided to install additional power outlets inside center console. This location allows for convenient charging electronic devices hidden from the curious people outside. When getting out of the car you do not have to remember to unplug and hide them. At the same time, this location allows relatively easy access for passengers in the rear. Power to the relay and outlet goes directly from the battery. The installation consisted mainly of pulling wires. However, drilling a small hole in the interior of the center panel was necessarily in order to pull wires for the socket. I bolted the socket using two screws. The fuse is located next to the battery.
I opted for the switched outlet, which operates only when the engine is running. This way I do not have to worry about discharging a car battery when parking a car. I used 12V wire from the existing left outlet in the front panel, the one depending on the ignition, as a switch power connected to the waterproof relay. On the other side, it is practical to have outlet powered even if the key is not in the ignition. A switch between constant and switched power was a solution. I installed On-Off-On switch in the console in the close proximity to the new outlet. Additional benefit is that having an OFF position in the switch allows me to power off any connected devices without disconnecting them from the outlet.