Anyone know what code requirements are for linking together smoke detectors and cables to motion sensors for alarm panels? (preferably in Chicago, where it seems everything needs to be in pipe)
Smoke detectors and motion sensors do not have dedicated rules in the NEC. State and local building codes typically address the requirements, if any, for such detectors. Your answer will be found locally.
Not sure what you mean by linking smoke detectors and motion sensors.
With alarm systems that I install (Canada) we either run separate, 12vdc smoke detectors and place them near the mandatory mains-wired ones, or use an approved relay that goes at the end of the interconnect chain for the mains-wired smokes. From the relay, we run back to the panel and that provides the smoke detector signal. Advantage is, less stuff stuck to your ceiling, and less smokies to replace when they expire.
As for motion sensors, if you're talking about security ones, they have their own wire (usually) run back to the panel, either station-z (4 wires, untwisted) or cat 5/cat 5e.
To the extent the NEC has anything that might apply it would likely be the low voltage control sections of the code.