Those are what I was referring to as the Hippo Hands. There are a lot of different types, some better than others, from what I've read. Both in quality of how they're put together and also how easy they are to deal with - clearance of controls, getting hands in and out, etc.
I think it's recommended to use some time of plastic/rigid hand guard along with the warmers because wind can push against them on there own and cause problems with your levers.
I don't have the need so didn't look into them into much detail. But I know Hippo Hands are popular. There is also a guy on ADV that makes them and I think they're pretty popular. I can't remember his name but he sells tool rolls, bags, saddlebag liners and such. Storm Industries.