I know – this sounds silly, but anyway:
We lost both of our old cats this year, and by pure coincidence we got a new cat 2 weeks ago – it’s a cat that was living outside a OAP home where my mother-in-law lives. The cat had been bullied by another cat at the home, and has been living outside for the last 6 months. It made a appearance a few weeks ago and my wife offered to give it a home with us.
And so Neffie move in to our home, and has started adopting us, as cats do.
Last week she managed to escape when a caller came to the door, followed by a anxious chase around the neighbourhood – without us managing to find her. And as a result we bought a GPS tracking collar from pawtrack.com after some discussions around the size of the collar. This was the smallest one we could find on the market.
Here she is

And you can see why we were concerned – the collar is not exactly small. We were afraid she would not take to it.
But there has been absolutely no problems, she does not seem to mind the collar at all, and gladly let us change the battery every 3 days.
It is a small price to pay for keeping the family happier that they know where she is, and that she has not gone back to her old woods.