If they were small enough units, a single function device controlled from elsewhere might work out OK. However, I'm talking about devices 2 mm x 2 mm in size, then and several per unit.

They've got to receive a signal from the "outside world" and relay it to the main controller, then respond to a message from the main controller and act upon it by causing some action, e.g. close a switch (relay, SCR, TRIAC). Since they ought to cost <<$1US in production quantity, one could have a sensor module and an actuator module together in the same device, provided the entire device isn't much larger than a small coin. It must be inobtrusive, ultra-cheap, and operate throughout a house or apartment. Range on the order of 10 meters is probably a minimum, but range over 20 meters would be objectionable. Range over 25 meters would be a killer, since you don't want to interfere with what your neighbor is using. Some provision for that has to be made anyway, but I'm looking for a cheap, small, simple RF link that might fit, if there is such a thing.

RE