Now THAT is cool!
(will I need an Apple tv to do that?)...
Yep, you'd need an Apple TV. But, at only $99, it's a small additional investment for your Slingbox setup.
When I downloaded iOS5 on my iPad, I was skeptical of the quality I'd get (considering it was wireless) but I was very, very surprised. It's literally the exact same as connecting the iPad via HDMI. And, because the Slingplayer app supports video out, the wireless signal automatically fills the entire screen.
It's truly incredible.