Thanks for the tip. We will update the page. The basic idea is that 70% of the calls we make daily can be replied with a yes/no/location (Where are you?/Should I bring milk?/Are you coming for the dinner? etc) Knock app tries to simplify this problem, if both users have knock installed whatever message the user sends is captured as a (Simulated) call on the other screen with the message overlaid. Instead of (answer/reject) there are (yes/no/location) options. Like a normal call, the phone rings for 60secs within which if you don't respond it becomes a "Missed knock".