How does the Space Replay record audio?
It seems to be possible to record with the shield using a library called waverp


  WaveRP is an Arduino library for recording and playing Wave files with
  the Adafruit Wave Shield. It records 8-bit mono files at 4,000 to
  44,100 samples per second.


Some details adafruit blog:


  It records 8-bit mono files at 4,000 to 44,100 samples per second.