Now there's a project for all you budding scientists out there, design a
cat flap that can read microchips ;-)

Incidentally, I've found the collars with a breakaway section to be ok,
apart from the fact my cat keeps losing hers ;-) I do like her to wear a
collar where possible though, just in case someone does find her, as my
name and phone number are written on it and people can contact me direct
rather than having to go through the process of finding someone with a
scanner to read the chip.

Ivor