https://vimeo.com/54501076

• Arduino Uno R3
• Makershield (with mini breadboard)
• Parallax PIR Sensor (rev B)

• GND (on sensor) to GND (on shield)
  
• VCC (on sensor) to 5V (on shield)
  
• OUT (on sensor) to Digital pin 2 (on shield)

Open File > Examples > Firmata > StandardFirmata
And run it on your arduino, that's it!

Run

ttMove/ttMove.pde

It'll take a few seconds for the sensor to warm up, but it should be working fine!

Right now, Processing 2.0 is in beta, and not a stable build. To get this to work I had to use Processing v1.5.1 (the last stable build)

When I first tried to connect Processing to Arduino, I got this error:

WARNING:  RXTX Version mismatch
Jar version = RXTX-2.2pre1
 native lib Version = RXTX-2.2pre2

I found this extremely useful post from kobby on this Processing forum thread.

To make this happen