I saw this on the iMac configuration page - it is a $19 option.
http://store.apple.com/us/configure/MB952LL/A?mco=MTMzNzU5ODc
Apple Remote
Control your Mac from afar with the sleek aluminum Apple Remote. Play, pause, adjust volume, move forward and back, and access menus while playing music and video.
Learn more
The Apple Remote gives you total command of your music, photos, videos, and DVDs from anywhere in the room. It works with Front Row a menu-based, full-screen interface to make accessing the digital content on your Mac as simple as navigating your iPod. When you press the Menu button, your desktop fades and the sleek Front Row interface takes its place to give you control over your music in iTunes, your photos in iPhoto, the videos in your Movies folder, and your DVDs. Turn up the volume. Shuffle. Skip to the next chapter on your DVD. Play a slideshow, a home movie you made in iMovie, even a movie trailer.
http://store.apple.com/us/configure/MB952LL/A?mco=MTMzNzU5ODc
Apple Remote
Control your Mac from afar with the sleek aluminum Apple Remote. Play, pause, adjust volume, move forward and back, and access menus while playing music and video.
Learn more
The Apple Remote gives you total command of your music, photos, videos, and DVDs from anywhere in the room. It works with Front Row a menu-based, full-screen interface to make accessing the digital content on your Mac as simple as navigating your iPod. When you press the Menu button, your desktop fades and the sleek Front Row interface takes its place to give you control over your music in iTunes, your photos in iPhoto, the videos in your Movies folder, and your DVDs. Turn up the volume. Shuffle. Skip to the next chapter on your DVD. Play a slideshow, a home movie you made in iMovie, even a movie trailer.