If a lower graded i&has part is fitted to an i&has then it lowers the overall grade however fitting an unrelated switch to signal something else isn't i&has
Smoke detection in yhis case would be classed as ancillary devices and would not need to be disconnected.
However they are not the same as a 5839 fire alarm. But i have smokes and Co on my own alarm
Bear in mind that if you extend that time your bb is still going down its just waiting till its down for the time set. Most people don't use the Internet 24/7 but your alarm is.
you need to get out more dd
surface knight grade 3 push set with buzzer
https://www.securitywarehouse.co.uk/catalog/intruder-alarm-c-36/intruder-alarm-ancillaries-c-36_46/knight-grade-3-surface-final-exit-set-switch-black-p-3909.html
flush version
https://www.securitywarehouse.co.uk/catalog/intruder-alarm-c-36/intruder-alarm-ancillaries-c-36_46/knight-z30-grade-3-flush-ss-final-push-to-set-switch-p-2556.html
If one of us could say that, I'm sure it would already be in development. Sky Google or amazon will control the mass market for security, they will sell it better than any of us could. Then it will cycle round again, the insurers will be miffed, the police and we will still be around to carry on....