alt Hacker NewsRegular pairing, advertising and control likley use Bluetooth LE for simplicity and battery life. Streaming or transferring video likley use Bluetooth classic for increased bandwidth.
These are two different protocols with different radio behaviour.
So beyond detecting the glasses themselves, which seem like the focus of the project; detecting recording is feasible at the point of transfer to a phone.
The issue is distinguishing it from any other high bandwidth Bluetooth device nearby, such as headphones.
They don't stream to your phone when taking a video or picture. The data is on device and transferred later. It also uses wifi direct not BLE. It seems many many people on HN have absolutely no clue how the meta glasses work lol, there's barely any accurate information in this thread.