As mentioned, the best place I've found is either the camshaft sensor (if equipped) or the crankshaft sensor. It is low current, doesn't require extra relays, and has the effect of disabling the injection and the spark. Basically this tells the computer that the engine has stopped and it responds by turning off the spark and the squirt.
http://ecomodder.com/forum/showthrea...tml#post102167
I've tried about every kill switch scheme imaginable and I like this solution best so far.