Speech recognition webservice that scores the accuracy of one audio clips vs. another?

Question

Does such a thing exist?

Building a Rails based web application where users can upload an audio file of them speaking that then needs to be compared to another audio file for the purposes of determining how similar to voices are. Ideally I'd like to simply get a response that gives me a score of how similar they are in terms of percentage (e.g. 75% similar etc...).

Anyone have any ideas?

Thanks