That metal can is the remnants of an old wired alarm system. It is being repurposed, the wired sensors are being translated into wireless 345Mhz signals.
That resolution products device up top is likely an RE208, which is their wired to 345Mhz translator. It is the same type of device as the 2GIG TAKE-345.
Here is a video going over the TAKE-345 installation to give you an idea of what this does.
I cannot view any real details of the board in the can due to its orientation in the picture, but it would be a 12VDC power supply and battery charging circuit. The backup battery would be for the wired sensors.
You could reuse any 345Mhz sensors and the RE208 takeover module with the 345Mhz version of the IQ Panel 2+ found here.