In these instances we charge a flat rate of $100/mth for a SFR - that covers collecting rents & paying bills, ensuring services are delivered, monitoring the property and the occasional simple/light maintenance.

Our nephew has a 640 acre ranch and they use their drones to monitor the cattle, food and water supply. 

This is being challenged in courts, so monitor it, but that alone could take a while.Cash for keys is truly your best option.

There are many people involved in this thread that are far more educated and intelligent than myself, but one strategy I'd highly recommend is closely monitoring REO/Foreclosure Auction listings on the MLS/Auction sites.

Mine can set door codes, message (or call) guests, schedule cleaners, adjust the thermostat, monitor my cameras, & call a plumber just as easily as a local PM can, for 1% of the costI wrote much more about leveraging offshore assistants in this post here.

Seems to me that cost should lead you to ensure water use is better monitored.

Monitor what they do with the subject.

Cameras were installed above the driver to monitor the passenger section (this was before they were so readily available on Amazon).

There is a doorbell camera so she can monitor who comes and goes as well.

Try another model.To answer specific questions you posted: Noise monitors are available that can be mounted in a room.