Stemoscope and fetal Doppler are very different, from the working mechanism to the intended use. Stemoscope is intended for recreations while fetal Doppler normally is for medical use. Here are some details.
|Ultrasound||YES. Fetal Doppler uses ultrasounds. According to the U.S. Food & Drug Administration, the effects of excessive tissue heating and cavitation caused by ultrasounds are not known (source).||NO. Stemoscope does not use ultrasound.|
|Gel||YES. Ultrasound coupling gel is needed.||NO. Since no ultrasound is used, no gel is needed.|
|Natural sounds||NO. Just provide an audible simulation of the heartbeat.||YES. Stemoscope amplifies the real heartbeat sounds, which are natural.|