Mrs Weasley's magic clock
Harry Potter novel illustrates position tracker with single screen (clock) and multiple beacons. Arrows on clock are meaning
Each of Weasleys can carry a GPS receiver and data transmitter, connective enough to cover big locations area (LTE, 3G or such).
Decoded data is shown on screen. Screen can also track direction of beacons movement.
Variant: linking to city map.