A 'hush' button
If you have a smoke alarm that keeps going off when you are cooking or burn the toast, never take the batteries out thinking you will put them back in later when you have finished. You could easily forget to put them in again putting you and your family at risk.
You can get smoke alarms that have a hush button which will automatically silence the alarm while you are cooking and will automatically reactivate it again. The alarm usually reactivates itself in 8 minutes or so and will work properly in case a real fire breaks out.
Emergency lights
Useful if the fire has knocked out the fuse on the lighting circuits.
An interconnecting facility
This ensures all the alarms will sound when any one of them detects smoke. You will probably need to ask an electrician for help with this one.