Nice Balls

After two prolific months - thank you very much - and 240 posts, I'm finally blogging about something I've absolutely positively no ID of. LOL. What're these rubber balls used for? Massage? Decoration? They look like colorful sea urchins to me. I know they glow (internally) when you squeeze them, but - again - what's their purpose? Can someone please enlighten me? Gracias!