Thanks for your feedback. We're aware of these problems and do take them very seriously in determining if we can actually build a useful and viable product. We are focusing on a small subset of well defined data types and plan to introduce a system for users to easily create their own custom data types for tracking.
We are targeting a more general audience that already uses journal and habit tracking apps available on mobile devices. With this in mind we don't seek to include all possible data types that might be relevant to more "hardcore" tracking enthusiasts right away. We are also working with a psychologist to help determine the few most commonly relevant psychological metrics as well.
Another consideration is that what users hope to get out of tracking does vary widely. To start we are focusing on a few predefined health and mood goals to help curate insights to users and look to also slowly expand this into a more robust system; however, from our initial interviews we have identified weight loss, mood improvement, lowered anxiety, and gym performance as the most important health goals we will be trying to help users achieve.
I will most certainly keep this forum updated on our progress moving forward. We're currently building out the MVP based off our customer discovery interviews. If things don't work out I will also definitely post a "lessons learned".