This contraption was labeled as "Catapulting seat" in Danish and is sold as an aid for standing up from chairs.

The text on the label says that it is "the easiest way to stand up from any chair", "lifts up to 80% of body weight", "from 45kg up".

I can already see a granny being catapulted across the room with this contraption - or a grandchild! Really "clever" idea ...