20 points
Article said they were using Bluetooth and a app on play store / app store I assume the app measures the signal strength to determine the proximity to the devices. Maybe some laptops don’t turn off Bluetooth in their sleep state or people just weren’t putting their laptops to sleep? Could pickup tablets or phones forgotten in cars too.
-1 points
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As he said, that only works if the device is on, which would be really odd in a car. I’m not aware of any that keep comms on in sleep, since those are typically high power draw.
7 points
There are various sleep modes and it looks like Bluetooth can be active during some of them.
