This is possible, but requires different wiring to light switches, to provide power there (which isn't common) and for manufacturers of replacement switches, bulbs etc to care about security.
The former isn't something which is happening yet anywhere that I know of (in the UK at least, even in new-build houses), and the latter needs pressure from consumers which isn't happening for anything in the internet-of-things space yet :/
(edit: don't try to use markdown in HN comments, however automatic it has become for you :)
