Really good idea for an app. My only wish is that the data was local only. It seems to me that the temptation to monetize this very valuable data will be irresistible. Although it's been normalized over time, there is something very strange about trusting a perfect stranger with arguably some of the most sensitive data of your life. And yet this has become standard, so I think you're on firm ground. But I ask- should this really be firm ground? I think it's up to us technologists to make solutions that do the right thing even when our users don't know what that right thing is.