Motion sensors (PIR), beam sensors and hand triggers for activating prop controllers.
Icstation 5V Light Sensor Module Receiver for Arduino, High Level Output, Work with Relay Switch, Non-Modulator(Pack of 5): Amazon.com: Industrial & Scientific
Laser Security System Infrared Beam Sensor Motion Detector Outdoor - from USA | eBay
Laser surface motion sensors | SPEETEC 1D | SICK
Smart Laser™ Sensor Activated Green Laser/Light Combo