radiators and chilblains
I think there is good evidence for that, but radiators have to be hot.
Not that I heard this but it was an urban legend that: if you put your feet in a po it would help with chilblains. I think it did depend on there being contents and what those contents were!
You used to be able to get a tin of chilblain ointment, it had the look & consistency of soft beeswax and a different smell. Don't remember it working that well.
To keep feet warm in the cold snow (and presumably ward off chilblains) we were told stamp our feet as we walked. That seemed to work on the warming front, can't remember doing those kind of analyses on chilblains - I was only 6/7 at the time.