PBS showed on Science last night how automatic "on the fly" pitch correction is being used by a lot of singers. It is so good it does not change the characteristics of the voice. Don't remember the name of the software however.
JJK
Melodyne is the latest and cheapest. Not realtime, for that you want the Eventide box and friggin deep pockets. It would appear that Melodyne can sort of work in Vegas judging by discussions in the audio fourm.
I suspect these work on single channel sources. I'm not sure much can be done when there is a mix with an on-key instrumental and a slightly off key singer.
I LOVE Melodyne! Melodyne lets a so so musician and singer like me sound like I actually know what I'm doing. It gives you control of so much more than Autotune, and does it without sound nearly as fake. Melodyne is to slightly off key and off the beat musicians and singers what Photoshop is to slightly overweight and wrinkley models. It is just a wonderful program.
Totally FWIW, I was reading that the latest trend with big money producers & artists is to make it sound like auto pitch wasn't used... It's gotten so common, that's one way to stand out, plus it helps the artist's rep, implying they're not one of the crowd of pretty faces that can't carry a tune.