I just had an idea, wondering if anyone has done this (or if you even CAN do it).

In the industry I work in, its pretty common to have remote monitoring devices for all sorts of things, ie: temperature, water flow, etc. The devices that do the monitoring are relatively cheap and many are wireless.

Has anyone implemented anything like this in their rentals?

I am envisioning a small array of sensors that report on each unit's temperature and water flow. The temp sensors can actually be integrated into the thermostat circuit as to limit the max temp - Is it legal to cap your units at 75F max? They can also send data to a remote computer / server so you can check on temps vs. time, water flow vs. time, etc.

I think if you offer internet service to your tenants this would be a nice way to keep an eye on things (as you need an outbound connection to report stats). Crazy?