Our Story
I am Dionysis Kastellanis, a runner and iOS developer based in Cyprus. I was training for a half marathon with an Apple Watch Ultra 2 and putting in months of consistent work. I had no way to tell whether any of it was making me faster.
The gap
Every running app I tried showed what happened on a single run. Pace, distance, heart rate, splits. But none connected that data across months to answer a simple question: is the same effort producing faster pace over time? To me, that trend is the clearest signal of whether training is working. I could not find it anywhere.
At the same time, the Apple Watch hardware had reached the point where its sensors rival those in dedicated running watches. Cadence, stride length, ground contact time, running power. The native Workout app surfaces all of it, but the experience is still built for general fitness. There was nothing on watchOS designed exclusively for runners, with the kind of customization and structure that serious training requires.
As an iOS developer, I was in a position to build both: an analytics layer that connects months of training data and an Apple Watch workout app designed specifically for runners.
Reddit and early users
I shared the first version on Reddit, in running and Apple Watch communities. The response was immediate. Hundreds of runners said the same thing: they had been looking for exactly this. Threads turned into a feedback loop. A subreddit grew around the app. My first paying users were Reddit runners who had followed the build from the start.
That community shaped the product. Feature requests, bug reports, training use cases. I did not design Pace It in isolation. I built it alongside the runners who use it.
What it does
The analytics layer tracks your pace in each heart rate zone month by month, surfaces your Training Load Ratio, derives personalized training paces from your last 60 days of running and rolls it all into the Pace It Index, a single 0 to 100 fitness score that reacts to real changes in training.
The Apple Watch app is a running-exclusive watchOS experience with 40+ metrics across 5 fully customizable screens, structured workouts with interval execution and a dashboard that syncs with the iPhone analytics. I built it to be the running watch app the platform was missing.
Who it is for
I built Pace It for runners who train with intent. Runners who know what heart rate zones are, who care about whether their zone 2 pace is getting faster and who want to know if their training load is in a productive range. It is not a tracker and it is not a coach. It is the layer in between: the one that connects months of data and tells you whether the work is paying off.
Privacy and pricing
I built Pace It so that all performance analytics are computed on your device. Your runs from Apple Health, including routes and heart rate recordings, stay on your phone unless you export them to Strava, and Pace It's usage analytics do not include them. If you connect Strava, the Pace It server stores and syncs your Strava activities to deliver them to your phone. Any device or platform that connects to Strava can feed data into Pace It this way.
Pace It is free to download with a generous free tier. Deeper analytics and the Apple Watch workout app are available through a subscription, with a 7-day free trial and a lifetime purchase option.
Pace It is independent and self-funded.
Frequently asked questions
What is Pace It?
Pace It is an iOS and Apple Watch running analytics app. It tracks pace at heart rate over months, surfaces your Training Load Ratio, derives personalized training paces from your own data and rolls it all into the Pace It Index, a single 0 to 100 fitness score.
Who built Pace It?
I did. I am Dionysis Kastellanis, a runner and iOS developer based in Cyprus. I train with an Apple Watch Ultra 2 and built the app because no existing tool could show whether my training was producing results over time.
How is Pace It different from Strava or Garmin?
Strava tracks individual runs and adds a social layer. Garmin shows what happened during a session. Pace It connects months of data and shows whether the same heart rate is producing faster pace over time. It answers a different question: not what happened on a single run, but whether training is actually working.
Does Pace It work with Strava?
Yes. Pace It syncs with Strava, so any device or platform that connects to Strava can feed data into Pace It. You do not need to change how you record your runs.
Is Pace It free?
Pace It is free to download with a generous free tier. Deeper analytics and the Apple Watch workout app are available through a subscription, with a 7-day free trial and a lifetime purchase option.
Does Pace It store my data?
All performance analytics are computed on your device. Your runs from Apple Health, including routes and heart rate recordings, stay there unless you export them to Strava, and our usage analytics do not include them. If you connect Strava, the Pace It server stores and syncs your Strava activities to deliver them to your phone.
Who is Pace It for?
Pace It is designed for runners who train with intent. Runners who know what heart rate zones are, care about whether their easy pace is improving and want their data to show them something useful rather than just logging another run.
If you have questions or ideas, or just want to talk about running, I would love to hear from you. Reach out at support@paceit.app or join the community on Reddit.