Hello, I read your job description very carefully and am very interested to work in this project because my experiences and skills are great fit for this position. I have rich experiences with EE design and development include Medical & Health care device, wearable device. so are you gonna develop TENS device? what kind of TENS?
There is simple TENS and complex TENS (has many functions).
For example it can be include ;
stimulates Vitamin D production, stimulates deep relaxation, promotes wound healing and deeper sleep, promotes cell repolarization, Blood electrification (promotes blood cell membrane potential), Brain tuner(promotes better concentration and drug resistance)...etc
But these functions are depends on requirements of the customer.
It will be need ESP32 or LRA/ERM, BLE device, vibration motor, graphic LED, motion detection sensors such as 6 axis, 9 axis accelometer sensor, Piezo actuator etc.
Also the micro current and proper frequency production will be very important.
I am sure i can handle this project to the end successfully and hope to discuss in more detail with you for this project. Although i can suggest more information for this project but i can't write anymore here.
I hope you are going well.
Best regards.