@Michael Butler: have you considered getting yourself a GMail motion account?
On a serious note: there are a few markets where this would make a lot of sense; for instance 3D modelling, where a mouse is usually inadequate. Even just being able to switch views, or rotate a model using - say - your free hand as a complement to the mouse would open a number of interesting scenarios.
For the general public, I'm not sure it would have a lot of traction. Aside of the (somewhat paranoid) perception that geturing may not provide the same level of privacy we have with a mouse or similar devices, I'm not sure I would want to be caught in public miming in front of my laptop. This might become socially acceptable someday, but I already got my fair share of stares when bluetooth earpieces weren't all that common, thanks. 
