[gosub100]

Then what? Run 50-200 feet of wire back to an Arduino? Or buy an Arduino and provision it for every smoke detector in the house? How do you power them? Another wall wart?

If audio fingerprinting can identify Miley Cyrus in background noise in a crowded bar, certainly it can identify the symmetrical piercing monotone of an alarm.

[withinboredom]

An arduino BLE, 18650 battery will probably run you about 50 bucks (retail, one-off). From experience, that will run for at least 4+ years in low-power mode -- maybe even decades. Announce a BLE service with the alarm status.