🚀 go-pugleaf

Easiest and cheapest way I can think of is to go to the
nearest discount home center and pick up some infrared
motion detector-controlled outdoor lights. (Due to the
large numbers sold, the full floodlight kit is actually
cheaper than the detector module itself!) I would install
one of the flood lamps as usual, and wire out from the
other port on the box to the pyro effects. You could 
wire a squib directly to the 120 volt line, but better,
add a small transformer (~12 V) and burn the squib(s) with
the output from that. The remaining lamp would just be 
part of the effect, as well as providing a proper series
resistance to the detector module. The low voltage would
also then be useable to power a short-range FM transmitter
for the alarm.

Dave