Self-reliance is an admirable practice, but at times we all need a back-up. Using some commonly available electronics, open-source software, and spare parts from your garage you can build your own robotic sentry gun. An automated sentry uses a live camera feed in conjunction with a number of servos to acquire, aim, and fire on potentially hostile targets. The sentry I developed for RECESS uses an improvised shot gun as the "dispenser." The single shot may be considered a limitation, but so as to act as an intelligent booby-trap. You can add other "dispensers" to your own sentry for varied defense strategies.
The software in my sentry is based on this open-source project, and many hours put in with my good friend James (who is WAY faster than I am on a road bike).
here is a short video demo:
Notes for optimal use:
Save Energy - Once the sentry is calibrated and set to guard your bunker door, use a timer to boot the sentry into operational status automatically - at the times you need it most.
Take Control - I recommend using a VPN, so you can remote in to the controller computer from your network or the Internet. This allows you to see through the Sentry's "eyes" in real-time, and/or strike the FIRE button manually.
