Straight from the Engineer

More specifically, the engineer sent his parts list for the playback unit. Suppliers are listed in the sidebar on the left.

1. The Arduino Leonardo: instead of the Uno because it's a bit cheaper
and maintains compatibility with another component.

2. Sparkfun's MP3 Player Shield for the Arduino

3. 2 gb Micro SD Card

4. 100k resistor

5. IR LED

6. IR sensor

7. Coby CSMP16 Mini stereo speakers

8. Sony CycleEnergy portable USB power supply

I have some questions of my own:

a) The container for the finished unit
b) Switches for on/off, calibration, volume controls
c) IR Sensor range