Each system of measurement has it's own advantages and disadvantages.
Typically the electrical ECG systems fall down due to muscle activity
causing interference and/or sweaty/hairy chests making the leads fall off!!!
I've done many an ECG in my time and even with good filtering software,
occasionally it's almost impossible to get a reasonable recording. And
that's when at rest.... exercise makes it even worse....
Pulse-ox finger/ear probes are fine as long as there is a goodly blood flow
happening. This isn't a problem when you're exercising normally!! The
problem then is more physical ie the clip gets in the way.
Of the top of my head, a reasonable third way would be to strap a simple
microphone onto the chest over the heart. I wonder if a flat piezo disc
would surfice.... I'd filter the output using a bandpass filter to remove
extraneous noise (ie speech) and voila. Not sure if it's been done that way
before but for simply testing the pulse rate a full ECG/pulse-ox solution
appears overkill.

Ben

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