There is 'Cloak' for iPhone and some other alternative for both Android and iPhone.

I blogged about their first paper back when it was news. Might be interesting to review at least because I blatantly copied two of their graphs. Graphs that seem to document solid correlation. I think the causality is quit obvious too. The "we're always just three meals from anarchy" rule of thumb. The societal mechanics are obvious. Can any of you skeptic commenters actually refute the correlation and the causality?