I guess you absolutely need a computing power beyond the ability of a wrist held device to distinguish your strong heartbeat between rest and walking/running condition, so it would have, if screenless, to be compatible with iOS or Android.
Maybe an investigation of actual sampled data of people with anxiety disorder would indicate that it can be done without AI and fit all in a screenless device, but I'm a bit doubtful.
I guess it can be done with the current smart watches and phones all is software, I don't know much about AI but you need a bit of AI, most probably running on the smartphone, but yes it can be done.
Coding often can become a (burnout) trap. Fascinating in the beginning, and over time it start to become misaligned with your inner motivation and you burnout. Take some time for you alone and your inner motivation will come on the surface, follows that.
Maybe an investigation of actual sampled data of people with anxiety disorder would indicate that it can be done without AI and fit all in a screenless device, but I'm a bit doubtful.