Are you after a system that you can assemble yourself, lego-like? No black box for a "controller", no proprietary pieces, standard kinds of wiring, etc? Standards (of some kind) throughout?
Sounds like: ONVIF (for cams, other sensors), ethernet wiring & ip-based (for any sensor), software (on any hardware platform) that controls everything. Solutions for relays & other specialty requirements, such that you assemble & wire your own "devices" to do something, and tie it back into security system.
I looked at this a few years ago, and at that time, it was possible to assemble an entirely open-source security system, bypassing the usual proprietary commercial vendor/suspects who only wanted to sell a black box system managed by their installers (like the home market suspects). Install your own cams from any vendor, your own door locks & access software, wire everything with ethernet cabling.
The controller software was sold by many vendors, with the usual "free piece" (controls X number of devices), then "paid piece" (controls unlimited, etc). Ran on any platform (windows, linux, etc). A few entirely open-source controller software packages (should be more these days, given Github & such).
Is this the goal? And for home use only, or commercial?