Here is a system capable of detecting intruders and getting their attention with soft foam darts. The Autonomous Sentry Turret does not need any human input. It comes with a modified electric Nerf gun mounted on servo mechanism. The system is powered by Intel Edison. You are going to need:
- Intel Edison with Arduino breakout
- Electric Nerf Gun
- PIR Sensor
- XT Connectors
- Adjustable Regulator
- and more
The above video shows how this system works. It is always possible to make it more painful for intruders. Aleator777 has shared more information about this project on Instructables.