I spoke to my aunt on the phone (she's currently in Spain and will be there for another week, travelling around in a cute little borrowed camper van, and after that she and her partner will take another week to drive to the netherlands with lots of sightseeing), and I sold her the whole idea of obtaining cheap sensors for me as an exciting scavenger hunt

She took the bait quite enthousiastically, so I expect I'll know all about sensors in Spain and France in the near future. And have a drawer full of sensors