I can't attest to the functionality of any of them as I know of nobody that has one.
Here is a couple LG units:
and it seems Haier also makes a unit:
This seems more of a European type design than a US one. Since we believe if we didn't invent the idea there must be something wrong with it, I suspect the US manufacturers are simply not up to speed yet. We have always lived in a world of excess (at least since I was born) so a separate unit that takes up much more space would be the American way. A compact efficient unit is something we would expect them durn furinners to use.