Why are there so few smart, hardwired smoke detectors?

[WallyR (Wally)]

There is a thread about it here.

Cavius smoke detector integration?

I have now tried frequencies spaced 50 kHz apart from 868.0 MHz to 870.0 MHz (i.e., 868.0, 868.05, 868.1, 868.15, …), but I get nothing. It has taken me a couple of days. I presume that the smoke detectors transmit on a regular basis, and presume that waiting 15-30 minutes at each frequency should give me something if they are, in fact, transmitting within such an interval. Do you guys also use the hub, or do you just have the smoke detectors? I have the hub and have paired the detectors with t…

The use of rtl_433 with HA is documented in many different threads and there are different ways to integrate with it.
The trick is to get a receiver device that is reliable.