Bad actors, and any WiFi capable hardware in your house. There's an official spec for it[1], and some routers already have the option built in. I remember seeing papers about this over 10 years ago, someone at MIT did it for a paper.

Philips Hue also has it built in to their newer lights, where they measure the Zigbee signals. They call it MotionAware[2]. Basically anything with an antenna and a bit of compute is able to do this now.

[1] IEEE 802.11bf-2025 [2] https://www.philips-hue.com/en-hk/support/article/motionawar...

Can't they already do that by snooping on ARP traffic on your home LAN? Failing that, if they can get whatever shitty wifi chipset they're using to enter promiscuous mode, they can also sniff all STAs that are in the vicinity, and with some ML they can probably figure out which MAC belongs to your phone.

Even having three security cameras around the perimeter of your house can allow quite precise location and activity detection inside the house via their audio steams.

Those mics can be quite sensitive.

They already knew this from your cell phone not being in airplane mode.