We actually have several hot socks in multiple places so that we always have access to one. We have been using these for years, and they are so much more effective and convenient than heating pads; no cord, you can move around wherever you want, and the rice inside will conform to the body part where it is placed.
I have seen others suggest dried beans rather than rice, DON'T do it!! Made that mistake one time, and my whole house stunk for the rest of the day.
And for small bumps and bruises, freeze leftover condiment packages. Perfect size for fingers and toes.