I was reading a book the other day where a scene was described where the cat had an electronic sensor around its neck and when it approached the cat flap it would automatically open.
I really thought this was joke, I've never seen or heard of an electronic cat flap before, so I took a look around and, sure enough, they do have 'em! It's meant to be safer than a manual cat flap. So which burglar can fit through a cat flap we want to know!
Anyway, while I was researching, and if you really want to know, I came across this great video on how to install a cat flap. Enjoy, it's fun.