Kinda cool, but honestly, I don't see it catching on. First of all, they misunderstand how I use my contact list:

"If you want more control than that, Ketchuppp lets you block certain people who you never want to have spontaneous catch ups with. If that’s the case you should probably just delete them from your phonebook."

So you're saying every random person I have in my phone I should want to randomly hang out with? Absolutely not. There are only a handful of people on my phone I would want to spontaneously hang out with.

The use case where I see this being fun is having 10 or so friends on my "ketchuppp list" and being notified when I'm out drinking and they're nearby.