@scottjenson RE google maps, I hear you. This particular problem could be solved by an app which remembers your speed, then displays the concentric rings. It assumes internet access/cached maps, GPS data and a device capable of displaying it — what if the device transmitting the information was a pedometer/similar which knows my speed but not location, has no internet access or way of displaying maps?

I’m a fan of more ambient approaches like this because they enhance my own senses (in this case my poor sense of timing) without trying to run my life, as apps seem to want to do. I see it as a fundamentally different approach; apps make me perform a task and give me output. Ambient information enhances my senses and gives me more context within which to make decisions.