nf17

I have an idea for an IoT product that may or may not work for niche audience. My background is software, I have developed Dotnet(api), iOS and Android apps and lead engineering teams. Although I have learnt basics of microprocessor, computer hardware etc during my school, I have more or less no knowledge of it now.

Where do I get started if I want to learn and make smart IoT products. I want to make a ring with a touch screen and a button. For starters, It will act as a counter using button and remind users(notifications) on particular time of the day. I also want to develop a mobile app as a companion that will help configure the ring, set reminders etc.

Where do one start to make something like this? Are there any open hardware that can be used for the prototype?

How do you design and document on the feature level(aka issue in github)? For example: If my team is tasked with developing a sorting feature in an e-commerce app. Are there design documents(like high level flow, technical approach, traceability matrix etc) that we can prepare before working on the actual task itself?

How do companies like MS, Google go about this?