I just did that for about $43 in my house. I’m in the US but they all work the same.
Smoke / CO detectors have 3 wires, neutral and hot for power and a common wire to trigger the other detectors in the house, it’s red in the US.
I used a $13 Kiddie smoke alarm relay like this one
and a z-wave dry contact like this one
On the relay you won’t use the gray and yellow wires for this application.
To one of the smoke detectors (I used my basement unit so I did not care about hiding the relay like I would inside the house), wire the black (hot) with the black of your system, the white (neutral) to the white of your system and the red (common trigger) to the red.
Then wire the blue (common) and the orange (rather salmon color) (Normally open) to the T1 and T2 connections of the dry contact.
In Smartthings create a (or several) custom smartapp within the Smart Home Monitor that will send you an SMS when the smoke alarm is triggered (hopefully you will never receive one). You can add other rules to that trigger, such as turning on all your lights, shutting off your furnace (I do that via the Ecobee DTH), turn on your bathroom fan to pull smoke out, turn on an outside strobe light and siren, etc…
It’s nice because it could potentially save your house from a bigger disaster as you can call the fire department right away before someone else realizes your house is engulfed in flames while you are not home.