Not sure about the smoke alarm.

People had them behind picture frames on the walls above beds, in alarm clocks next to beds, in the mattresses, and bed frames, he took off outlet covers so he could treat those areas, and down in the baseboard trim we took off that, to get behind.. we finally took up the carpet & pad, they were embedded in the wood carpet tack strips, we took that up .. so the bad unit was treated, and re treated,  and we didn't rerent that for 2 months.

[AKA - "STOP: My neighbor does not have alarm/Surveillance systems -You'll have better luck there" (Kidding!...

They can get in just about anything alarm clocks, behind pictures on the wall or bedside tables, and of course bedding, furniture anything stuffed. and stuffed animals.. 

Provide proper notice according to the lease and perform a quarterly fire/safety inspection that includes smoke/CO2 alarms, furnace filters, cracked windows, missing screens, broken locks or electrical or plumbing fixtures, holes in drywall, water/smoke stains on ceiling, missing wood trim or handrails, loose flooring/carpeting, general cleanliness etc.

Great question Scott.I have a BA in Psychology, and right out of college went into a full time position working with an alarm company.

Another good excuse is to check on the fire alarms.

This is a general response, naming attributes, based on your post and what I would want personally:-Monitored, police response -motion sensors in appropriate areas-cameras both indoor (public areas)  & outdoors - motion activated, records to cloud, holds for minimum 48 hours, w/ audio capability-remote light switch control-remote alarm mode settings : on, off, at home-remote lock / unlock entrance-remote doorbell camera (service, delivery interaction)-temperature & flood sensors around appropiate areas-alert capability (various) set for your concerns-ample exterior motion dection led lighting, some solar powered lights that illuminate all night-phone app that you are comfortable usingThere are more attributes I would want but I'll stop here. 

I think there are opportunities anywhere you live.As for bad neighborhood, I always invest in relatively bad neighborhood, that I will not like to live.However, that does not mean I am willing to invest to too low price market.If a large city has average sale price under replacement construction cost, that is an alarm to me.If one part of the city is low, but next neighborhood is way higher, I consider that an opportunity.You have to know the areas really well.I started buying REOs on the peninsula in 2009.

An alarm system is expensive for a short term use.We don't need any squatters moving in!