The Pressure Sensor Module incorporates a material called Velostat with the Arduino. This material adds more resistance when more pressure is applied to the material. This module also uses the RGB LED ...

It runs on an Arduino MEGA 2560 PRO (or similar microcontroller) and supports a wide array of additional hardware including pressure transducer, water level sensor, flow meter, OLED display, and more.

Novosund has created an ultrasound sensor that allows real-time blood pressure sensing without any cuff hassles. It is ready for smartwatches, and even rings.