Sometimes you can do the cold approach. As a 20 year-old college student, I really just wanted some career guidance to be able to eventually do what I wanted, work in the mobile-sphere. All I did was ask in IRC, and a few phone calls later I had myself an internship.
I realize this method is probably a lot more suited for the younger, college crowd, and it certainly won't work at every startup, but it worked for me!
Why did you choose to support Windows Phone instead of Android? With limited resources it seems like a waste of time for such a small percentage of market share.
That being said, I don't think the concept is as bad as others are making it out to be. As a college student, I know TONS of people who sell everything from textbooks to notes (might be a good pivot). Problem is, with the introduction of groups for universities, we have preset groups for stuff like this.
One thing I am worried about is a potential spam to groups that I'm in, which would only make me resent your project.