The little rice bag

I'm your little comfort bag.
Keep me by your easy chair.
Two minutes in the microwave,
I'll warm you anywhere.
I'll ease the aching in your knees,
Your feet, and twisted neck.
That arthritis in the hands,
I'll chase away, by heck.

On aching backs or shoulders,
Or legs or hurting heads,
Apply it cold or heated
For comfort, it is said.
Keep me very close to you
When chilly times begin.
Just zap me several times you see --
Together we'll have more "Vim"!