Pulse Necklace 21July2009
 Optical Heart Beat Circuits
Awesome digital and analog heart beat circuit - but quite complicated. I think this is by far the best thing I found.
Optical Heart Rate Monitor - dead simple, actually almost too simple to believe that it works, in fact they do a lot of magic in the software, and say that if the signal is noisy the BPM will be wrong.
Yet another project, with filtering circuit - looks to be in-progress effort at the time of the report, so who knows if it works or not.
Strobe the LED Idea - this page talks about how in some commercial light detecting circuits, they strobe the LED, and then have a high pass filter, and in this way they deal with ambient light fluctuations. But I don't know if the signal we want (reflectance difference due to pulse) would survive this treatment. Here is a High Pass Circuit.
Flashing earring heartbeat monitor - really cool armature idea!