Since you're a software developer why not just start by buying 9usd wearables and reprogram it, bluetooth with colored or black and white screen, heart rate sen

Since you're a software developer why not just start by buying 9usd wearables and reprogram it, bluetooth with colored or black and white screen, heart rate sensor and accelerometer built in. Lots of people have been doing that and adding new features. Hardware is hard if you don't have the experience.