My "foot-warmer" is a piece of fleece sewed in half about the size of a half pillowcase. At the bottom of this pillowcase is a sewn line about two inches from the bottom. In that tube is about a cup of beans. This is put into the microwave each evening before I go to bed. I tuck my feet into the pillowcase, and I go to sleep so much faster if my feet are warm.
I also have an arthritic neck, so I have another tube, about 3 X 12, this one filled with rice. They go into the microwave together for 99 seconds. That's enough to put me to sleep and make my neck feel better.
Beans have a different smell when heated, but after using that bean filled pillowcase for more than three years, that smell is gone.