For my sister's birthday, I wanted to make her a corn heating bag. I had some green fleece, and as I cut it out I decided to embellish a little.
These are simple to make, just pick up some feed corn (DON'T use popcorn!) from your local farmer's store, or rice will work as well. Fill a cotton bag with the seed, leaving enough room that it can wrap partly around feet, your neck, etc. Sew the bag shut, and create a case out of fleece, flannel, or something else snugly.
To heat the seed, place the cotton bag in your microwave for a few minutes (don't overcook) and insert it in the case. It will stay warm for at least a half hour, sometimes longer, and is a nice alternative to a plug-in heating pad. A sachet of herbs, like lavender can be included in with the seed, or you can sew a pocket on the outside of the cotton case for a little aroma-therapy.