After implementing a 30-Day Activity Calendar in EdgeFit, I wanted to move beyond simply displaying fitness metrics.

The next milestone was Personal Activity Insights.

EdgeFit is my privacy-first fitness companion built using React Native, TypeScript, HealthKit, and SQLite.

What's new?

Activity Consistency

Understand how many days have recorded activity across a recent period.

Weekly Step Comparison

Compare average daily steps across consecutive weeks, while accounting for missing data.

Exercise Frequency

Understand how many different days contain recorded workouts.

The engineering challenge

One important lesson when working with health data is that missing data is not the same as zero activity.

If a metric is unavailable, treating it as zero could produce misleading comparisons and insights.

That's why I'm focusing on explainable calculations and data-coverage requirements.

Why not use AI immediately?

I want to explore on-device machine learning, but first I need a deterministic…