Uh ? the mouse's purpose was always there : to interact with WIMP based UIs, which is doable with a keyboard, but hardly as easy as it is with a mouse. The fact that the mouse was invented at the same time as the WIMP concept should be a big clue to this. It took many years for it to become an essential tool for computer users because it took many years for WIMP to become the defacto standard in PC computing UIs. Both are tied together.
The question is now : What does this bring to the table as far as new UI paradigms ? It just seems to me to be a new way of interacting with existing UIs. Something a keyboard/mouse/drawing tablet presently do much better with much less arm fatigue than this thing. Unlike the mouse and keyboard and drawing tablets, this thing is simply hardware. It's not bringing anything new as far as UIs go, which is a definate requirement for new input paradigms.
The mouse was invented at Stanford Research Institute in 1963. PARC wouldn't develop WIMP around it until literally a decade later.