I am going to try to get down one idea per day using this blog. "One idea per day" comes from the Seinfeld "don't break the chain" productivity approach.
In the spirit of this effort, the first idea is a blog extension that automatically creates a "chain" visualization. There exist many apps for creating such a calendar generically, but it is always better to have the visualization grow automatically if possible. This could be useful for any event that can be sensed. Apple Watch does something similar with "Activity history", showing a calendar of activity events.
What if you could just attach a sensor to something that you wanted to make sure you did everyday? Let's say I want to learn an instrument. I attach a small sensor to it that is tuned to detect when it is played. I use a mobile app to set my goal every day for a particular sensor (e.g., "play for 20 minutes") then attach it. This would automatically create a "chain" for me on the app.
The problem is, of course, that practice does not make perfect. Perfect practice makes perfect. So how can you tell if you're doing well? Perhaps the sensor has a mic that pics up audio and has some basic analysis abilities to detect quality. If those don't work well enough, clips could be fired off to experts (that is, crowdsource the problem).
Could such a basic sensor be used to track other things in this way? Attach a motion sensor to a bike, to shoes, hats, etc. In this way you could solve the problem with many activity trackers: they fail to track anything that doesn't look like a step. Just attach a sensor button to things (your swim trunks, kayak paddle, etc.) and you'll get at least some data for every activity.