Hot leads device?

Hi, well, first i will apologise for any impropriety, i am rather new to 
usenet.

could anyone possibly give me/point me to any information on how the "hot 
leads" device works, for those of you that don't know what it is, it is a 
business card holder that sets the business card aflame when it is 
removed.  i have done some searching through various means (including a 
patent search) and come up with nothing.

my best guess would be that is uses something similar to a glow plug that 
is used in a model RC aeroplane, or perhaps just a spark gap?

thanks very much in advance for any help!