I cannot directly answer your question Dingo, however I suggest you investigate Smoke Alarm Legislation in your State.
I recently noticed that Queensland has new legislated requirements including the following:
To comply with legislation, interconnected photoelectric smoke alarms are required:
- From 1 January 2017: in all new dwellings and substantially renovated dwellings (this applies to building applications submitted from 1 January 2017).
- From 1 January 2022: in all domestic dwellings leased and sold.
- From 1 January 2027: in all other domestic dwellings.
https://www.qfes.qld.gov.au/community-safety/smokealarms/Pages/default.aspx
https://www.qld.gov.au/about/newsroom/smoke-alarm-legislation
Basically from 1 January 2017 onward any new or replaced smoke alarms must be interconnected and of the photoelectric type as per the applicable dates above.
I do not know how interconnected alarms can be installed to units without conduits and wiring, unless maybe someone develops a wireless type of alarm.
Rgds,
Allan