The fetoscope is the modern combination of both the stethoscope and the Pinnard Horn. It uses the practitioner's forehead, or in some cases hand, to conduct sound and has a more modern look to the whole device, being made from metal and plastic compared to the wooden Pinnard Horn. It does not use ultrasound.
I normally introduce the fetoscope around 22wks which is when I can pick up sound. I use this because as a midwife I try to utilize the tools that allow for the most least invasive care to the growing baby. We try to provide the most natural home for the baby and not distrupt the careful flow.
It's my belief that the baby and body has built in mechanisms to keep itself safe and it is hard to determine if over use of the Doppler can distrupt that.
Discuss this option with your provider and see if this is a good option for you.