Do you have a laptop with a trackpad? Do you wish you could take that trackpad and hook it up to your desktop instead of having a real mouse available? If you answered yes to the second question Apple has you covered now. Oh and I question your sanity.
But I also think this could be kind of useful. On one hand I’m not a huge fan of trackpads but on the other hand I’m a huge fan of the multi-touch features of my MacBook Pro’s trackpad.