Today I've had the second calculator in 2 years stolen. The calculators we use for study aren't cheap as they are those nice scientific ones. This is made worse by the fact that I don't have a job. Anyway, in changing the batteries on past occasions, I have noticed that there is a small cavity in the back. Is it possible to buy an affordable beeper that can be triggered by RFID? I had also thought about installing a GPS tracker, but I gather they can be quite expensive. Can anyone recommend a supplier of cheap beepers and/or small (cheap) GPS trackers? Alternate suggestions to prevent the stealing of calculators would be welcome too.

PS - Although I would be spending some extra money on security measures initially, I think that in a few years there would be a net saving of money due to the current need to shell out for new calculators every year.