I would like to have a fire alarm similar to the Manual Alarm Control Panel where you could define trigger and actions for the fire alarm.
For fast temperature measurement it would be nice to have a way to trigger the fire alarm based on quick temperature raising also.
Are you suggesting tying in fire/smoke alarms into HA, because you can already do that with automation.
Or are you suggesting tying in DIY sensors? I don’t think I would feel safe with the latter. As it is, HA’s manual alarm system is a bit delayed in responding and without good automation and scripting behind it (set up by the user) it’s really nothing more than an elaborate trigger.
In my opinion, I think you would be wise buying a DSC security system and Envisalink to couple that with Home Assistant. All the sensors that communicate with DSC are fully-supervised.