You will build a Borg costume; resistance is futile. Instructables user djsures constructed his version of the alien from painted hockey pads, an LCD screen, and pulsating LEDs. He carved the head unit from a soft block of foam and used a black headband to make it wearable – he’s definitely resourceful. Here are some details on the electronics in the head piece:
The circuit is operating off my custom microcontroller board running a Microchip Pic 16F877a @ 20 MHZ. A little overboard for what I need, but it’s what my board is pinned for. There is a Sharp IR Distance Sensor on the front, a servo with a laser and many random LEDs. The servo moves the laser around randomly, until an object comes within 30 cm (1 foot) of the distance sensor… Then, the servo aims the laser at the object directly in front. The idea is the laser will scan around when I’m walking, and aim itself at someone when I stop to talk to them. The LEDs randomly flicker, as if loading and processing information.
Read more at Instructables.