A novel item if test-gear, difficult. How about a fetal heart simulator, I do't mean an ECG simlator but an actual physical simulator, one that moves! How do people test fetal heart detectors, generally by wiggling the transducer back and forth a few inches above the desk-top. There must be a better way. How about mounting a waterproof speaker at the bottom of a tube, about the size of a large bean tin (that's A1 tall for those in the grocery trade), filling the tube with water, covering the top with a membrane and playing fetal heart movement shaped music into the speaker. Modern monitors use quite sophisticated algorithms to pick out the fetal heart doppler signal so ideally the signal should be a good one, though I guess a swept sinewave might do. Good luck.
