Right.
Still not useful at all for decoction. Decoction involves pulling off a portion of mash and boiling it. This is done not just to heat the mash, but to aid in the formation of melanoidins. In cooking speak, you're making a Maillard reaction. It's not going to happen sub-boil. You need to boil.
Still essentially a HERMS system. Actually, I guess depending on the model, it could be closer to a RIMS, but it's still something that already exists in homebrewing. You could use it to help hold mash temps, but I have the feeling it would only be good in BIAB applications where your grist is really thinned out. Even then, given the sheer volume, I doubt you'd be able to raise the temperature much. Unless you're using a really big immersion circulator, you would probably just be able to hold temperature.
I would also be concerned about the heat source. It looks like most of those units are using high density elements. You don't want that. You want an ultra low density element to avoid scorching or over caramelization. Look over at the electric brewing subform for more info.