While it only takes a right-swipe and a thumb-typed message to meet someone, it takes months to know them, and by that point, you're committed to them out of sheer inertia rather than any human desire. It's the one problem an app could never solve. Unless ...
This app would immediately identify a jerk. Luckily, modern technology makes this more realistic than you might think. The Internet makes it easier to detect assholes by amplifying the hell out of them. Most people aren't imaginative with their profiles when registering for new social websites, so "Asshole Alert" would use their dating profile, or facial recognition from a photo you've taken, to find and scan all their other online accounts. It would then alert you if they contain certain keywords.
"Yeah, I'm not ready for someone that into farm animal role play."
Social media is like a Geiger counter for human toxicity, in that your average asshole doesn't know how to type 140 characters without shrieking about his or her most depraved psychosis. Has your date called a stranger a bitch? Written about ethics in gaming journalism? Do they defend Dawkins? You deserve to know if racial slurs or threats of violence are bubbling away inside them, because after a certain length of time, they're going to spill some on you. This app would avoid more wasted time and bodily fluids than several wars. No reason to spend hours working out if someone is an asshole if they've already volunteered their nights and weekends advertising that to the world.