T-stats for cast iron radiators

Hi all- I heard at one time that you can get individual T-stats and install them on cast iron radiators; is this true and is it recommended? The radiators are the kind that are individual units if you will made from cast iron sections and go up to the window stool. They're not the kind like the more modern base board type. TIA for the help, Bill-

t'stat

I have not seen any advertisements for them in years, but they used to have thermostatic valves that replaced your wheel handle ones on each radiator.

Thnx HJ

It was some time ago I heard about them. Any idea if there're worth doing? I'm by myself and don't the heat so high in every room. I'd like to save on heating costs if I can. Thanks-