I like the GFI idea ALOT, but am a lil more scared with essentially shorting a high voltage circuit than a low voltage circuit.
To clarify, you will NOT really be shorting the AC.
The resistor I mentioned limits the current to be just high enough for the GFI to detect. According to Wikipedia:
"In the United States, the National Electrical Code requires GFCI devices intended to protect people to interrupt the circuit if the leakage current exceeds a range of 4Ė6 mA of current (the trip setting is typically 5 mA) within 25 ms."
To make darn sure the GFI trips, cause 10ma to flow. Ohm's law tells us we need a 12k resistor. That resistor will be dissipating only 1.2W, which is perhaps not the "short" with obligatory sparks and smoke you might have been picturing.
And it will be doing so for less than 25ms; so although a common 1/4W resistor would survive that current for that time, I would use a 2W resistor just in case the GFI is defective and fails to trip.