Step 2: Parts

Picture of Parts
IC1, IC2, IC3 H-Bridge Motor Driver 1A, SN754410 (Sparkfun #COM-00315)  or L293D (Digikey#497-2936-5-ND)
R1 - 1K Resistor (Radio Shack #271-1321 or Digkey #PPC1.0KW-1CT-ND)
LED1 - 3mm Red LED (Digikey #160-1708-ND)
S1 - Slide DPDT Switch (Digikey #401-2000-ND)
JP1 - 2x6 Male Header Connector, Straight
JP2, JP3 -(2) 14-pin Male header, extra long pin or use shield stacking headers (Adafruit ID#85)
JP4 - 2-pin Male Header Connector, Right Angle
JP5 - 6-pin Female Connector, Right angle
16-pin IC Socket (Radio Shack #276-1998)
Multipurpose PC Board with 417 holes (Radio Shack #276-150)

The RevIO or any kind of Arduino
Note: In case of using Arduino or others Arduino Clone you needed to make the Motor Control Board to match those Arduino.

Other parts:
2 XBee Modules I got the Series 1 from AdaFruit
2 Xbee Adapter Board from AdaFruit

Alternativel part:
Bluetooth Modem - Blue SMiRF Gold (Sparkfun# WRL-10268)
or Bluetooth Modem - Blue SMiRF Silver (Sparkfun# WRL-10269)