We're currently performing research into the MCG Project, and we've finally hit pay-dirt. We figure we can perform an MCG using data packets rather than raw analog signal. Here's how we're thinking about doing it:
We send a data packet with a pseudo-random number encoded in it. We open a window shortly after this message is sent - initially a very small time interval after - and listen for the echo, checking that its the same PRN. If it's received in this time window, we know we have a signal. We can vary the window from very short to longer time intervals in order to get a broad spectrum of dopplar times. From this - we can perform some signal processing to determine where the heart beat is.
It's a very high level idea at this point, and much needs working out. The importance of this idea is more relevant to the hardware side of things - it's finally feasable to use consumer level electronics! We just need to look into enabling full-duplex communication on the same frequency with bluetooth/802.
More to come.