The picture to the right shows some of the connectors available on the rear on the Pixy (CMUcam5). There are 2 R/C servo outputs available - these can be programmed to control the micro-servo's available in the Pan-Tilt mechanism kit.
This allows the Pixy to control the Pan-Tilt of the mechanism, which in turn allows the Pixy to physically track selected objects/colours as shown in the video below ....
More info can be found on the Pan-Tilt mechanism at: 1. Assembly Guide
2. Running the Pan-Tilt Demo