DJ hero has been in development for almost 2 years and there are few details, still, but they recently launched a website at www.djhero.com. There's not much to see there yet, but an area to sign up for updates and the platforms it will cover: Wii, PS3, Xbox360.
Slated for release later this year the title will include a laptop DJ "mixing" peripheral to add to your plastic instrument collections. Internet rumors suggest that DJ Shadow and Daft Punk may be included as playable characters as well as tracks from Tiesto, and that there may be a battle mode that allows use of guitar peripherals in a face off.
But don't take my word for it, go to the site and let them dump the news into your own e-mail along with other fun advertising materials, to be sure.