Another overlooked problem is that when the backup battery gets low, it makes the alarm go off to make sure you know the battery is low.

The margins just aren't there to pay a third party to handle every minor problem I might have.While I mostly run long-term single-family rentals for families, I just answered a service call in my househack at 11:30 pm last night to change out faulty batteries in a carbon monoxide detector.

Ring cameras are good and their batteries last a long time.

so a $90 service all and an $80 capacitor fixed well over 1/2 of most issues.There are lots of issues that aren’t even that complicated… Batteries in the thermostat going dead, drain lines, getting clogged with dirt and goo, drip pans that get full from the unit sweating too much or not draining properly, bad thermostats, etc.Occasionally, you will get either a leak, or a bigger part that goes bad that will cost in the $200 to $500 range… fans and motors going out, etc.Home warranties are worthless… they will take 3 weeks to fix your AC.  

My approach would be to use a plugin sawsall (more power than battery) and cut sections out as needed unless it's a water wall in a bathroom or kitchen.

I'd love to do solar but the sun doesn't shine at night here and battery packs just aren't sufficient for my electrical load for night service. 

My first thought was to change the batteries in a fire/smoke alarm, carbon monoxide detectors, etc. - or some other electronic device. 

I don't see that little niche factored into those reports. 30 years ago, if you wanted to call across country, you called after 10pm because it was a lot less expensive and you called from a phone with a cord on it that was attached to a wall. 30 years ago, the idea of a private person flying rockets into space and owning a battery operated car company would probably have gotten you put into a white jacket in a comfortable room somewhere in a place with a nice name like Bellevue. 30 years ago the idea of a self driving car was popular... on The Jetsons.

Supposedly the wifi connectivity will drain the batteries in the lock faster than other methods. 

How is battery life?