pauluk,
You mentioned the AC remote-control relay that was operated by shorting a low-voltage winding.
Over the years I've needed exactly such a relay, and I remembered them from dozens of 1960's vintage hobbyist electronic magazines, but for the life of me, I couldn't remember what they were called or who made them.
And why don't they make them any more?
One of those in an X-10 size wall-wart with a pair of screw terminals would have hundreds of applications (think magnetic reed switch and fluorescent strip light that turns on when closet door is opened). Isolated, low-voltage, inherently safe, CHEAP!
