For the inside you might want to incorporate an infra red and motion detection system. This helps with false alarms. To make the alarm sound you would have to have the motion detector violated and the infra red sensing a rise in heat(someone's body heat entering the room) to set off the alarm.
Just a thought,
John Wright
PS. We just installed one of these in our church and it works great. The motion detector picks you up at the door, but won't go off until you step inside and the infra red picks you up. With the old one it had motion only and a dog walking by the door on the outside would set it off. It's a shame you even need one on a church, but you do.

Kam,
Sounds good but you do have to feed him occasionally unless you want him to be really hungry when the "would be intruder" arrives.
John Wright