With over two years in the making Max for Live allow users to create and edit their own devices. Essentially you can create whatever you can think of (in terms of sound design) from unique synths and effects to hybrid hardware / software music machines.
Max for Live will retail at $299 / EUR 249 or if you own Max 5 you can get Max For Live at the discount price of $99/EUR 79.
More info: http://www.ableton.com/maxforlive