Other materials needed would be a small amount of fabric to make your rice bag.

I made this to help comfort my aching cold hands. You can warm it in the microwave and slide your hands in to warm and soothe them.

It is done by knitting a long rectangle and then picking up stitches and knitting down to the middle to form a pocket on the inside to hold a bag of rice. That way all you have to do for washing it is turn inside out and remove rice bag.