I want to build a wifi robot with a camera. suggestions?

[dwind62]

I have reasonable skill with electronics/ programming, I started out with a Polulu 3pi robot and gained some great programming experience with it, then I built a Failurebot 5 , I had a lot of fun with those projects, but now I want to build my own robot. I'm not an engineer, and I have a very small budget for it (i plan to scavenge as much of as I can from parts I have lying around, so, I'm looking for a inexpensive, and function able plan .
I want to build an AVR based, differential drive Autonomous robot, that has a camera mounted on it, and I'd like it to be able to send videos to my laptop via WIFI. I guess I'm thinking of a robot security guard for my shop. Maybe I can use a motion detector to allow the robot to remain in sleep mode until it detects movement. I assume I'll be fabricating the boards/circuits that are practical to do with through-hole only soldering skills.
my questions are: Should I go DC geared motors or servos? how powerful do the motors have to be? any suggestions on a wifi board/camera? the materials I have available for the platform are 1/4" plywood, 1/4"  clear acrylic, or 1/8" thick aluminum sheet. Which material will give me the best strength/weight benefits?
Is it practical to mount the camera on a servo that tilt up and down, and use the drive motors to position the camera side to side?  Thanks in advance for any help/direction to get me started with my project.