FlowChair

My idea (when I was 10) was to make a chair that had a bladder in the seat upon a column of fluid in the base.

Sitting in the flowchair produces pressure through a variable opening and fills the cushion to fit yer butt perfectly.

Once the pressure is equalized somewhat a valve shunts additional pressure into small nubs within the seat (or a big one or two ;) that slowly inflate over a set with a dial time period. Once fully inflated these nubs provide incentive to get up and stretch, or massage like sensation to make sitting longer less fatiguing.

Once the sitter gets up, the fluid returns to the base through spring action like a normal desk chair.