I have been playing with reverse engineering my cavius wireless smoke detectors for the past couple of months, and I figured some here might find it useful.

I used an ESP32 running Arduino code to interface to MQTT over WiFi and an RFM69 module to receive and send signals to the cavius detectors.

Here is a link to the code and wiring. Here is a link to some good documentation on the protocol, running at a different frequency for Europe, our ones run at 926.365MHz 

Alternatively if you have an RTL-SDR device (cheap USB TV tuner that can be used as a radio receiver) you can use RTL_433. Here is the command I was using to receive the information using RTL_433:

rtl_433_64bit_static.exe -f 926365000 -s 250000 -p -1 -R 179