The two prominent players of touch + pen are Wacom and N-Trig, but Atmel want's a share of the pie with their new technology called maXStylus.
The industry's highest performing stylus for tablets and handsets. The new active stylus solution from Atmel delivers unprecedented capabilities including Windows 8 compatibility, 1mm stylus tip, and simultaneous touch and stylus operation. Combined with Atmel's industry-leading maXTouch solutions, which are powering millions of smartphones and tablets today, the maXStylus family offers and unparalleled human interface by providing simultaneous touch and stylus functionality. Referred to as multiSense functionality, this feature enables advanced gesturing such as zooming in/out while writing and scrolling; page flipping while scrolling; and selecting a tool or content.
Such an easy description to read... Basically what's unique about their technology is that they allow touch and pen input at the same time. Wacom and N-Trig do not allow simultaneous touch of pen and touch, usually once the pen is close to the screen the finger touch is disabled. (example 1, example 2). You can spot this feature on the video when Mr. Yassir Ali zooms out with the finger and pen touching the screen.
I'm not aware of any tablet that currently uses the maXStylus. Hopefully one comes out in 2012.