Have you heard of the Craigslist Killer?

A problem with local marketplace websites and applications is the lack of the building of "credibility" for it's userbase. That is, there is no method to signify how many transactions the seller has had and the rating for a respective buyer and seller.

Meet Rialto - A marketplace for university students that provides a localized buy-and-sell environment that everyone can trust. Users "unlock" reviewing by meeting at a location the seller posts and scanning a QR-code at that location. This scanning also increments the seller's transaction amount, giving the seller more credibility.

Locations that are agreed to meet on are either "verified" or not. A verified location is one that is on the grounds of an educational institute.