To help you narrow down the best fire alarm to buy online, could you let me know:

Get real-time alerts on your smartphone the second smoke or carbon monoxide is detected.

Are your existing units into the wall or battery-operated ? Do you also need carbon monoxide (CO) detection built-in?

"This sets up a repeating notification for as long as the smoke alarm is going off... its also how I've got certain lights, like my porch light, to start blinking when the fire alarm is going off." — Reddit