Amazing $3 3D printed stethoscope

This is really designed for the third world but anybody can build one. Est. cost is just a few bucks and tests showed its acoustic performance to be on par with the gold standard in medical stethoscopes, the Littmann Cardiology III. It sounds like they spent a lot of time on the design (3 years) transforming this from a toy to a serious device, despite it's humble origins and low price.

https://hackaday.com/2018/03/17/3d-printed-stethoscope-makes-the-grade/