If, in the future, you were to ever walk into someone's bathroom and see only a sink, you might want to look under the sink cabinet and see if they have the toilet stashed in there. This is the Hidealoo.
Now, if you were to purchase a home and find it has a bathroom that is so small you can't open the door all the way, or if you have a half-bath that could be a full bath if there were a little more room, or you are adding a bathroom and have a limited footprint for any reason, the Hidealoo might be the perfect solution. Maybe you have no extra space at all, but your family could really use an emergency second toilet in, say, the laundry room. You can see some of the situations where this kind of toilet would come in handy in their brochure.
However, the Hidealoo requires that you have plumbing for a wall-hung toilet, which is not all that common in the US. Yet. Wall-hung toilets are gaining ground in new construction, and may well be worth a conversion if you are pressed for space and really want another toilet in your home. -via Nag on the Lake