Now you mention it, Mr. Red, I think I'll have to change my doctor. The stupid man takes my heart rate at my wrist and once, in an overnight test, even at my little finger. If he even doesn't know where the heart is....

Seriously, you could of course take the heart rate at that place as well for the heart rate is perfectly correlated with the ebb and flow in the blood flow even at the periphery of the body. A bit out of phase, of course, but as you surely know a measurement of a frequency isn't affected by that.

Wolfgang