Bluetooth on a mobile will work without a SIM card.
You could treat it as a metal detector. You use the Bluetooth only when you need to. The next time your keys decide to play hide and seek maybe?
The Tile app seems to think Bluetooth should be on all the time. I do not which meant the keys l misplaced in the garden wheelie bin this week were according to it some distance away initially, having obviously been picked up someone else's mobile while I was cycling to Sainsbury's. Took it a while to then decide they were far closer but as the review notes they are not wholly precise in their GPS locating (others may be better). It was indicating they were at the back of house behind my neighbour which did initially make me wonder if a Magpie had picked them up and dropped them but then wandering around outside I suddenly got a strong signal from them and then even stronger one. The audio from them was limited to short burst rather than a continuous sound which otherwise would have helped locate them quicker, since resolved by fitting a new CR2032 battery.
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