Hot/Cold pack

My mom got this hot/cold pack that you can reuse, with this pastic pack with a clear colored gel inside. Nothing special, right? Well that's what I thought. The differnece in this one is, it has a piece of thin metal inside, a small strip, that when you squeeze it and form friction, the gel inside reacts to it. It begins a chemical reaction that spreads throughout the whole thing, from the strip outward, and turns the soft water-like gel liquid inside, into a much more solid opaque gel, that's very very HOT. It stays like this for HOURS, and when you're done with it, you put it in boiling water, and it breaks down the gel into the old form it was, and you can reuse it again. It BLEW MY MIND. If you want to use it cold, just toss it in the freezer. Oh, this was for the bruising/cut/swelling/etc on my leg. I'd post pictures that I took of it today, but I'm afraid it would scare you all away... so I'll post after I recover. =P