Aside from the motion sensor parts, there's also the bright light, to mess with people's night vision. For this, I got 4 super-bright LEDs, and did monstrous things with solder to produce a 5x2 header, that was fully connected along the long side. This gave me the 4 LEDs connected in parallell. This is pretty bright with the 5v applied from the analog output of the Arduino:
The final result will be built on an Arduno Fio board, which only has a 3.3v signal (It's powered off a 3.7v LiPo battery), so I'll need to amplify that somehow. I'm thinking I might try to power the board and LEDs off a regular 9V instead, or have the LiPo powering the board and the 9V powering the buzzer and leds, gated on the signal line of the board with some transistors. I may be of course talking out my ass. I'm going to pick up some various transistors over the weekend and experimenting. My guess is the gate and emitter of a transistor need a common ground, which won't work with using separate power sources. We'll see.
Of course, deadlines, help. I'm supposed to be using this thing next saturday. So, full steam ahead.