After a long hiatus, I decided to resume working on this project.
I bought a USB power supply, that easily powers the Pi with the camera module and wifi dongle running.
The 6xAA battery pack is now dedicated to the motors.
I also wrote an android app that communicates with the Pi over wifi.
The video shows the current state of my project.
I made the app with a smaller screen in mind, so it looks a bit strange on a tablet.
The laptop shown at the end of the clip shows the server software running on the Pi.
The next step will be to make use of the Pi's camera module. The plan is to either include a live feed in the android app,
or to write a web interface instead.
After a few failed attempts, I decided to ditch the lego.
This is what i ended with.
Camera module mounted on a small servo motor.