A software known as VocaListener has been out for a while, and demonstrations have been posted here and there. As for as what is known, there is still much to do with the software before it's finished and up for download.
This software is used with VOCALOID1 and VOCALOID2 voice synthesizers. Much like the software MikuMikuVoice, VocaListener detects the parameters, such as dynamics, in a person's singing, as well as lyrics. These parameters and lyrics can then be imported into the voice synthesizer, and then the magic happens. Any VOCALOID voice bank will have an impressively similar sound to the singer imported to VocaListener.
Here is an entire website with examples and demonstrations.