How to get started with Microsoft PixelSense
Here is a great interview you should listen to.
Basically, you will likely need to purchase a PixelSense machine. The Developer edition is $15,000. At the moment, it is difficult to get your hands on the bits unless you went to PDC but I'd imagine that will change and there will more opportunities in the future.
There is a simulator, but it was only available to attendees to PDC. One of the input methods was to use TWO mice, if I recall correctly. It looks like an interesting experiment, we'll see if it actually takes off.
As for the hardware, you can buy it here. edit: now here
To just test drive the actual unit, head down to Vegas and see the unit in Harrah's casino.