OP, it's debatable whether you'll find any ghosts in the house using that probe, :-). What
it's really doing is using the probe wire to pick up the magnetic field given off by alternating
current in the power mains. See the part where it says "a magnetic field circulates around
a current-carrying wire" in this link, except in the AC mains, it's alternating.
http://www.khadley.com/courses/lectures_ph102/lecture5_28_10.aspx
The first FSM schematic circuit was tuned for 100-300 Mhz, which is useless for you, the
2nd was more general - just a basic amplifier. In your diagram, the Leds are just the display
device, and you would want to insert an amplifier between the probe and Arduino A/D
converter pin. Basically that "probe" is just a big antenna.
The following ckt would probably work, using an MPF102 FET bought at Radio Shack.
http://www.sciencelobby.com/field-effect-transistor/junction-fet-as-an-amplifier.html
Use the 3.3M where it shows 1M, use the probe instead of the 0.1 uF input capacitor,
forget about the 22 uF cap, and use a short to the A/D converter where it shows the 0.1
uF output cap. Supply power from the Arduino 5V pin. So, just MPF102 and 3 resistors.