The governing code is the general building code- the NEC is silent on the issue.
The smoke alarms can be wired to any power supply that meets the manufacturer's specs. They must have battery back-up. When one sounds, all must sound.
I am not aware of any low-voltage residential smoke alarms. There are such things for commercially montored, central alram systems. I cannot see any reason why an AHJ would not allow you to install such a system in a house.
In that regard, the "special" residential requirements are intended to allow for an affordable system. A central system, with sensors, horns, and strobes, would certainly cost much more than the roll of romex and $5 detectors currently available.
