Klm,

You might want to run your ideas past a prototype maker with a background
in biomedical engineering. A local engineering school or university medical
center would be a good place to look for this sort of advice. If this device
goes inside the body then safety issues are really important. Knowledgeable
advice may save you a lot of time
A double boiler may fill your bill since it will not get above 100 C and
yet will keep your components out of the water.

Dave M.