I am experimenting with making microwaveable warmers. The ones I have been working on use corn and are for sitting around reading in the evening, and warming my hands/desktop in the early morning. Later I’m going to experiment with other grains. If memory serves, both rice and flax seed have been used. I would think – for walking on – either one of those could be worked into something nice. Especially the flax seed; which is flat, smooth, and small; should be nice.