A concern would be that the batteries would be dead forcing my tenants to be locked out. 

Other than that, soap, some batteries AA & AAA & 9v, notepad pen dishwasher tabs a smelly candle dog treats poop bags TP paper towel a colouring book/ crayons if they have a kid some Lysol wipes and such. $20 gift certificate for pizza joint hand written “moving sucks, this may help”.

Get the smoke detectors with 10 year batteries, put one in every bedroom, every hallway, and everywhere but the kitchen. 

The battery gives up about halfway through the night.I don't think $14 is too much to pay for the security of lights.

This means they pay for things like light bulbs, batteries for smoke detectors, etc.

-Change smoke and carbon monoxide detector batteries at move-in.

The trap was removed and it contained 1 toothbrush, 1 pen, 1 eyeliner pencil, 1 AA battery, and 2 hair bands.

great app...however, if the battery is dead, i'm assuming you're SOL, correct??

Most have lights that run on batteries (a small red light showing it is on and "recording") and they even have motion ones that move in a sweep pattern.

A Nest warning alert in the winter costed the landlord $125 to trouble shoot finding out the battery was low.