Working in the industry as a Building Surveyor i thought id set the current regulations down for everyone who cared. the rules are: all smoke alarms to be hardwired with battery back up, installed by registered electrician and installed in accordance with Australian Standard (AS) 3786.
in terms of location. the current Buidling Code of Australia requires smoke alarms to be located outside of a bedroom (i.e. the hallway), above and below staircases leading to other storeys. You do not need one smoke alarm per bedroom. it depends on the layout of the room. if three bedrooms are off the same hallway you will only require a smoke alarm at either end of the hallway depending on where they lead.
smoke alarms to kitchen's are of course ill advisable and removed from design drawings prior to a permit being issued.
as said previously in the discussion people can put them wherever they want and yes it might indeed be wise to have them in bedrooms. keeping in mind fires only start by fire sources. what fire sources are in bedrooms apart from electrical, lighters, and the big killer... candles...???
hope this was enlightening for those who bothered to read lol. anybody else have questions on building regs pm me =P