Would you know if a dear, but seldom seen, friend happened to be on the same train as you? The Proximeter is both an agent that tracks the past and future proximity of one�s social cloud, and an instrument that charts this in an ambient display. By reading existing calendar and social-network feeds of others, and abstracting these into a glanceable pattern of paths, we hope to nuture within users a social proprioception and nudge them toward more face-to-face interactions when opportunities arise.