I decided on a whim to take apart an old smoke detector that desperately needed replacing, and after some ripping, I got to the guts of the thing.
Clearly the brains of the detector is that DIP IC on the right of the board: Motorola XC370696P. Here's a closeup of the part.
The internet is surprisingly quiet about this IC. Any insight on what this part is, or where the datasheet lives?