Kitty safe

Have you ever come home to find evidence of cats other than your own making themselves comfortable in your house whilst you're away? Or you're been woken at some ungodly hour in the morning because some neighbour's cat has decided to spend the night in your kitty's bed and your kitty ain't too pleased about it? I've had this issue to deal with and wondered how to resolve it. First, I hate putting collars on cats. I had a cat in the past who had a neck injury that I fear was caused from being trapped by the collar - he lost several whilst out doors. Second, I don't think the magnetic collar thing can be effective....how many other people have the same sort of cat flaps? Solution, why not use the signal from the ID chips they have. Bingo! Thankfully, a Channel Islands vet has manufactured an RFID device that makes everyone happy.