Central heating pipe stat,Technical question ?

going by a standard pipe stat what clamps onto a 22mm or 28mm hot water pipe and held on by springs,the trouble with this type of stat is that it takes a long time to switch on even when the pipe has been hot enough for 10 minutes,(is there a better type of pipe stat that switches on-off sooner)I have thought of a idea if you take apart a Mechanical Temperature gage what has a moving hand for the readings inside is a sealed curved tube what is filled with a special liquid when the liquid gets hot the curved tube tries to straiten out could this not be used in conjunction with a micro switch and be installed as a pipe stat,other people must have thought of this idea before me,if this type of pipe stat is on the market could you let me know.