Anything that requires the ability to detect if it's in the same physical space as another device / item of interest. Some common examples are: * guest mode d

Anything that requires the ability to detect if it's in the same physical space as another device / item of interest. Some common examples are: * guest mode discovery on a Chromecast * pairing to videoconference system (both Cisco and Polycom do this in their current gen devices), building control, wireless presentation system etc * a means for transmitting a 2FA code from a personal device for auth / payments * micro-location service - particularly for temporary events or spaces where BLE is not possible (e.g. embedded in FOH audio at different stages at a music festival) * proximity based peer discovery for mobile games You'd be surprised at how common a technique it is. I regularly face issues with environments that have had enough different devices all attempting to use some form of ultrasonic pairing / localisation etc that there's issues with interference.