Nothing substitutes for a good battery of questions and following up with references, but do you have any specific advice?

You plug in the receiver into an outlet where you want to be able to hear it, then put the battery operated button outside.

I save $$$ big $$$ every year because my lead tech takes the time to try to walk the resident/tenant through the problem they are having and resolve via phone if possible.My favorite hero call every time, is when it is 20 below and tenant calls with a furnace out issue, turns out it is simply the batteries in the thermostat, many people do not know that the thermostat in nearly all cases (except for a modern nest) are not direct connect/direct wire and are powered via battery.

That is easily solved by removing the batteries and plugging it and then plug it back in.  

On it you should have things like:House keepingWindow glassRodentsPlumbing/WaterCarpetSmoke Detectors (Change the batteries too)DrainsToiletsYou are trying to do a few things:Document/correct on going damageFind immediate issues that need addressed (water leaks, broken glass, infestations, house keeping issues etc) so you can issue lease violations or perform maintenance.  

The next time they back to the house the robber pull the meter out the meter socket trying to kill the power to alarm system put the system is equip with back up battery.

If there is a basement and it has a sump pump, I always be sure the pump is in good working order and has a battery back up.

The appearance is good without the need for a finish washer, the go in easily and have a torx head that avoid slipping.If you don't have one, an impact driver with two batteries would be a good investment for a job like this.

We don't have to worry about that, but I've had to move all the batteries for inside storage due to the heat! 

Steal the batteries out of the old ladys hearing aid and the problem is solved .