Andrew explained :
https://leakbot.io/

For Brian.

It's some kind of sensor that seem to detect a leak and send you
an alert on your phone.

How come it doesn't treat all water usage as a leak, including
when you are having... a leak ?

Andrew

They probably listen to the noise from flowing water, the flow will not
normally be continuous, unless there is a continuous leakage. Another
way would be to listen to the tick of a water meter, which should stop
completely for long periods of no water use.