Just to cut into the discussion: I don't know anything about EEG or ECG
waveforms, but you might also look into wavelet transforms (similar to
fourier, but while fourier relies on sine waves, wavelets rely on short
wave packets, and will result in a 2-d array describing frequency and
amplitude distribution of the original wave). I had a look into them once
for another type of data analysis (not on a PIC - something slightly
bigger), but had dismissed them in favor of a plain old
least-squares-method (for the time being).

Bye
  Markus