Advertisement from Seeed Studio in my email today included this device:
https://www.seeedstudio.com/Marvelmind-Indoor-Navigation-System-Starter-Set=
-HW-915-868MHz-p-4296.html


Marvelmind Indoor Navigation System Starter Set HW (915/868MHz) Supporting
Ultrasonic and ToF
50Meter max range and +-2cm precision.

Seemed relevant to the conversation.
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