That loop is a magnetic sensor that detects when a high permeability material passes over the loop because of the inductance change of the loop. Kinda like an electromagent.
These things are also used (in the US at least) to trip on-demand traffic lights, especially turning-lane lights. This is a huge problem for motorcyclists because most bikes are mostly aluminum and don't have enough ferrous metal to trip the sensor.
One enterprising fellow is selling a relatively small (but powerful) magnet that will trip the sensor. Magnets are much higher permeability than steel, even, so a relatively small magnet will work. Small enough to carry around.
The only problem is -- it's a magnet! I don't know many computer people who want to lug around magnets. On the other hand, I think the empeg is pretty well shielded, and most people use optical media now, so... you might want to try it:
Green Light Trigger
Jim