A side channel is a channel through which information may leak because of the physical instantiation of an algorithm. It's not much of a stretch to include "things which let us manipulate the world" in that; do you have a better term? I thought the meaning was obvious, but apparently it's not: by "side channel" I here mean "unintended means of affecting the world by a mechanism derived from an accidental consequence of the physical implementation", by analogy with the standard "information"-related "side channel".