It may be that her landlord installed it wrong, but landlords (and homeowners) install an impressive number of things wrong, so a business that didn't depend on "amateur does X perfectly" doesn't sound like a bad idea to me.
The Dance of Smoke Alarm Supplication can still apply to smart smoke alarms: https://www.youtube.com/watch?v=BpsMkLaEiOY
However in what scenario does a landlord install a £100 smoke alarm when s/he can install a £10 one though? No landlord I've ever had would have done this -- given that over here bills are paid by the tenant a thermostat is usually not provided.
Homeowners can at least move them when they realise they have installed them wrong.
And when the price falls to £30, as happens with these things, a lot more will do it.
Not even on fire, maybe people are smoking inside when they aren't suppose to be. Maybe someone burns their food commonly and that needs investigated before they burn the whole damn place down one time. I can see lots of reasons for that.
Because very few things suck more than coming home from work and your house is burnt down because the smoke alarm wasn't heard by anyone and by the time the fire crews arrive it's too late. Happened to a friend of mine, house was beyond repair even though fire crews arrived 10min after a passing driver noticed the blaze.
How would you get your pet out in time if your CO alarm or smoke alarm went off when you were at work?
I find it odd that people are questioning the value of this life and death information while there are plenty of frivolous IOT devices.
My point is that the smoke alarm and the CO alarm should be exactly what they are simple alarms that allow occupants to escape in an emergency. Adding IOT capabilities doesn't add to the alarm functionality in sensible ways. However, it does risk introducing vulnerabilities. I don't want my smoke alarm to start sending spam emails (this really happened with a smart fridge a couple of years ago).
In the case of CO2, is it better to have qualified personnel attempt to arrive at 6pm after you get home from work and hear the alarm, or sometime closer to when the leak occurred and you were alerted on your smart phone? (I don't think emergency responders are twiddling their thumbs in the evening or there's light traffic)
In the case of fire, is it better to call the personnel before the retired lady down the street notices the flames and smoke while your at work??
In this case the ability to remotely check the alarm status from a self check, or to remotely snooze a false alarm while clearing the smoke can be very handy
I usually install two, and run a electrical line to one.
Yes, an app is fine if you burn food, and have the disposable income? I would rather see home owners spend the money on running a line to their smoke, and CO detectors though.