Here's the finished product!
I started by gutting a broken clock I found at an antique store.
I drew out specs for all the vector patterns and gave it to a friend who knew how to use Illustrator…
… and laser cut/etched those vectors onto wood! You can see the loose innards of the clock here – it's really just a Particle Photon connected via a breadboard to an addressable LED strip.
I used IFTTT (If This Then That) to define radii that would send messages to the Photon if my phone entered or exited them. (I would later walk the other 5 members of my family through the same process.)
Most of the rules are location-based (setting me to WORK if I enter my university library, HOME if I enter my dorm), but you can set other triggers too (set me to HOLIDAY if the forecast calls for snow, set me to MORTAL PERIL if the stock of the company I'll be working for next year drops too low)
some of the code and a to-scale wiring diagram
looking into the back of the clock, with all the LEDs sunk into crudely cut styrofoam
The back all sealed up again!
Et voilà! The glass in the hinged metal rim broke in transit, but I kept the metal there anyhow. The glowing B is black paint on acrylic, lit by the tail end of the LED strand hanging down, and it flashes a different color for each member of the family when it's about to update their position!