This Gun Robot project can monitor the entrance to your fortress and ward away any enemy attacks! The servo action seems nice and smooth, next step would be to make it IP based so that you could have the unit at work and control it from home.

"The bot is totally controlled by an external joysitck or joypad. The app uses DirectX DirectInput to get the data from a connected jystick. This data normally goes from -1000 to 0 to 1000, so some code was writted to re-map this to 1 to 127 to 200 (the servos range of travel). The joystics trigger button was re-mapped to some code that tells the trigger servo to goto X wait 10ms then go back to center."