Take a look at TextALibrarian.com. This was created by a small start-up mobile Q&A service called Mosio. They won the Mobile Category at SXSW this year. They have a number of beta library customers including Yale, UC Berkeley, University of Kansas, and UC Merced among others. There is a demo on the website that you can try to see how it works, including both sides of the conversation (basically you get to text in a question, and answer it yourself through the web interface).