Facelesstech made a light following bristle bot and wrote a post on his blog detailing its assembly:
Lets have a look at the hardware side of the build. Here is a bread board layout below. As you can see its just 2 bristle bots where the pager motor is controlled by a 2N7000 transistor which its speed is determined by the LDR (Light Dependent Resistors) and adjusted with a resistor trim pot. I also added a led to each one to show which pager motor is being activated, This makes it easier to see whats going on too.
Check out the video below: