I have actually been giving serious consideration to building a sentry turret with twin airguns. Mainly for the technical challenge but also to protect against the sort of thieving scum who exist in every city, not just Bristol. If they're going to break into my house, they take their lives into their own hands...
Because image-recognition-based IFF isn't the most reliable technology when homebrewed (or otherwise, for that matter) this little project has been dropped.
A remote-controlled turret has definite possibilities, but I might load it with tranquilisers instead.