I want something like an activity armband where I would like to add an bend sensor or EMG sensor for simple hand gesture recognition tasks. I could probably build it from scratch with arduino-like parts, but it will be much more bulky then the ones on the market and I would rather not reinvent those things that already do what I want. This is the type of device I am thinking about.
Is there an feasible task to try to modify an existing activity armband or smart watch by adding one of these sensors? If so, do you have any suggestions of what should be considered? Should I try something completely different? I am open to ideas. I have a background in Physics and Computer Science with an basic understanding of electronic devices but I am eager to learn.