Just a week after the teaser video was released, SlingPlayer for iPad (US$29.99) is officially available. This app lets you stream anything that comes from your Slingbox SOLO, PRO, or PRO-HD to and iPad via Wi-Fi or 3G. Thirty bucks is kind of high, and the app isn't universal so you're looking at sixty bucks if you want to toss an iPhone into the mix.
Note that the Slingbox Classic, AV, and TUNER are not supported for use with SlingPlayer Mobile. If you own one of those you're not completely out of luck; you can take advantage of an upgrade offer to save $50 on a new Slingbox SOLO or Slingbox PRO-HD.