Gloves with chemical heating

You know the small hard plastic cushions one can boil until they get soft to store energy in them to reuse later? Later, when cooled down, one bends them (bends a little metallic thingy in them really) and they heat up by themselves.

Why not make smaller such to insert into gloves and mittens? Especially for toddlers that don’t have the experience to keep hands dry and warm.
Sew a pocket inside the glove to keep the cushion.