Electro-Harmonix, producers of the BIG MUFF, make some of the best music effects boxes around. And the new Voice Box is amazing: it will automatically harmonise with whatever you throw at it. See for yourself.
Aside from Frampton-esque vocoding, the Voice Box listens for a key from any electric instrument input and then adds a symphony of harmonic backers of a gender of your choosing, all automatic-like.
I know how this will all go down. Just like Auto Tune, it will first be used by Cher, then be adopted by a thousand dancehall producers in Kingston, shortly followed by a dread-locked American hooksman, and finally, the trendmaster himself, Kanye. [Electro-Harmonix via MAKE]