I believe this is what Drew did with Dropbox and YC (if I'm not mistaken, in his application he said that he was going to follow through with Dropbox whether he got into YC or not). Granted, he is technical person, but (IMO) the simple fact that he was ready to finish his product, no matter what, showed a lot to the YC panel.
Some universities have classes that need real projects to work on too. If you get into a community college, there is probably a shortage of real projects for them to tackle while at a large university there will likely be a long waiting queue unless your idea is so above par (or you're famous or cool to work with) that a professor or dean moves it to the top of the queue.
If you're looking for more of a cofounder, there are websites or marketplaces for that: http://www.techcofounder.com/ or http://www.cofounderslab.com/ - I'm sure you can Google "find a cofounder" to find more.
Let's say your app is a marketplace of sorts. Your app need "buyers" to input data, store to a database, perform magic algorithm voodoo to find matches and then query "sellers" on the opposite side of the marketplace.
Don't do any of that to start.
Let a "buyer" input data, which is directly emailed to you. You then use your brain ("algorithm") to find matches and manually email those "sellers" manually with their matches. Further, don't program any of this. Use Wordpress for the site, WuFoo for the forms, etc etc.
People get way too hung up on the tech. Make everything as manual as possible to start, because that is the fastest way to realize your idea probably sucks (or, if you're lucky, only needs serious tweaking to make work)