I mean for personal use, airtags seem all right. But it's the ones that don't come with a warning that they're around that worry me.
I mean if you're paranoid, I'm sure there's detectors that can find bluetooth signals and whichever other technologies they use (I'm fairly sure GPS is passive, that is, they only need to receive satellite signals, not send anything).
Download the nRFConnect app and you'll probably be amazed at the number of BLE devices that are around you all the time.
Anecdote: I used to work for a company that did a lot of wireless wearable stuff and early on in COVID lockdown I had a Linux tool: bluetoothctl, running while I was testing some code down in the basement of my house. The first indication I had that my wife was home was the appearance of a Fitbit device in the scan, followed by a couple of unknown phones as she and a friend walked up to the house.
Not unexpected, but it was that sudden appearance of devices (I live far outside the city) that really drove home how much data we're throwing off all the time without thinking about it.
Wow, I was indeed amazed. I live in an apartment building, and I could immediately see more than a hundred devices! The list has everything: from headphones and smart watches to light bulbs and TVs.
I mean if you're paranoid, I'm sure there's detectors that can find bluetooth signals and whichever other technologies they use (I'm fairly sure GPS is passive, that is, they only need to receive satellite signals, not send anything).