Would you like me to give you some Ruby code that would emulate this functionality? I am fairly sure the size of the program would be less than 300 LOC, tops.
That is indeed a "little app". The 30-something line regex parser Pike wrote (http://www.cs.princeton.edu/courses/archive/spr09/cos333/bea...) ? Also a "little app".
There is no shame in solving a small problem, solving it well, and solving it concisely.
As far as being a "rehashing of other ideas"--how many hackathons have you been to on college campuses, and/or how many students doing mobile dev stuff have you chatted with, and/or how many people with a great idea for a local messaging app have you met?
This is not, will not, and never has been a novel idea. That doesn't make it worthless, that doesn't make it pointless, but it also doesn't make it new.
As for the "toy campus app": that's what this is...a toy application (small, concise, single-function) targeting primarily college kids (see the comparisons in this very thread to JuicyCampus).
I honestly don't understand why you're getting so defensive just because I'm not getting down on my hands and knees to praise the obvious genius and ingenuity and novelty that went into this (this is sarcasm, by the way).
I can respect it as a work on its own merits, but I will not afford it more than that.