Ran across this "StrikeMaster II Pro" during my web travels today which reinforces doors so that they are tougher to kick in. The video in the link below I think is worth watching. It is pretty compelling to see two blokes kicking away at a door repeatedly and it not budging with the StrikeMaster installed, then to see it cave in with a couple of kicks from a single person. At the least of it there is some mild entertainment seeing these guys put foot to door.
Anyone have a spare door I can try this on for when I have a bad day?
Where it can be bought: