Your data, plainly

Last updated: 18 October 2026 (Analyse with AI)

In short:

Your camera picture goes only from your phone to your TV, over your home network. It never reaches our servers, and we never record it.
Body tracking runs on your phone. To the TV it sends your rep results and the positions of a few body points, not pictures.
There is no account. Profiles and history are kept on your TV.
To link your phone to your TV, our servers keep a short pairing code for two hours.
Only if you press Analyse with AI: that workout's numbers (no video or pictures) are sent to an AI model on Amazon Bedrock to write a report.

Who we are

RepCast is a fitness app for Amazon Fire TV with a companion camera page that opens in your phone's browser. It was built for the Amazon Developer Hackathon 2026, and its source code is public on GitHub. In this policy, "RepCast", "we" and "us" mean the people who make it.

The camera on your phone

When you use Coach me on camera, the camera page on your phone uses your camera to see how you move. Body tracking (Google's MediaPipe Pose) runs inside your phone's browser.

The live picture is sent directly from your phone to your Fire TV over your local network, encrypted, using WebRTC. It does not pass through or get stored on our servers. To set up that direct link, your phone and TV contact a public STUN server run by Google, which sees their network addresses but not your picture. There is no relay: if your phone and TV can't connect directly, no picture is sent.
Body points: the positions of 13 body points (such as shoulders, hips, knees and ankles) are sent to your TV so it can draw your skeleton. They go over the same direct link, or through our live messaging service (below) when the direct link isn't available.
Rep results: for each rep, the phone sends the TV whether it counted, how deep it was, and any form notes (for example "knees drifted in").
We do not record video, take photos, or use your camera for anything other than the workout you started.

What goes through our servers

RepCast's servers run on Amazon Web Services (AWS) in the Mumbai region (ap-south-1).

Pairing. When you start a coached session, the TV asks for a pairing code. We store the code, a random channel name and the time it was made. The record is deleted automatically after two hours.
Live messages. Your phone and TV exchange messages through AWS AppSync Events on that random channel: rep results, framing hints (for example "step back"), body points when the direct link isn't available, and the set-up messages for the direct video link. These messages are passed on as they arrive and are not stored by us.
Server logs. Our pairing service keeps error logs for seven days to help us fix problems. We do not use them to identify you.

We do not sell your data, share it with advertisers, or use it to build a profile of you.

What stays on your TV

The names you add under "Who's training?", each person's workout history (date, move, reps, minutes and clean-form percentage), streaks, and any moves swapped in earlier versions are stored only on your Fire TV. They are not sent to us. To delete them, clear RepCast's data in your Fire TV settings or uninstall the app.

Voice

The coach's voice is pre-recorded and plays on your TV. RepCast does not use a microphone.

Analyse with AI

After a camera workout, the results screen has an Analyse with AI button. Nothing is sent unless you press it. When you do:

What is sent: the exercise, the planned sets and reps, and for each attempt whether it counted, how deep it went (an angle in degrees), how long it took and its form note; plus, for earlier sessions of the same exercise on this TV, how many days ago, the reps, the clean reps and the time. Also the session's pairing code and channel, so our server can check the request comes from a workout in progress.
What is never sent: video, pictures, body points, names or profile details.
Where it goes: our server (AWS, Mumbai) passes the numbers to Amazon Nova, an AI model made by Amazon, on Amazon Bedrock, which writes the report. Bedrock may run the request in another AWS region when Mumbai is busy (cross-region inference). Amazon Bedrock processes the request under AWS's terms; AWS states that Bedrock does not use your prompts or results to train models.
What is kept: we don't store the numbers or the report. The report is shown on your TV and forgotten when you close the app. Our server keeps an error log for seven days, and counts how many reports each pairing session has asked for (at most ten), deleted with the session after two hours.
The report is written by AI from numbers only. It can be wrong and is not medical advice.

Other services

The phone camera page is hosted on GitHub Pages, and this website on Netlify. Like any website, they receive your network address and basic browser details when you visit.
The camera page downloads the body-tracking model from Google's servers (storage.googleapis.com) and its fonts from Google Fonts. This website uses its own copy of the fonts.

Children

RepCast is meant for adults and teenagers training with a household. It is not directed at children under 13, and we do not knowingly collect their personal information.

Your choices

You can use Follow along without any camera.
You can stop the camera at any time by closing the page on your phone.
You can delete everything stored on your TV by clearing RepCast's data or uninstalling it.

Changes and contact

If we change how RepCast handles data, we will update this page and the date at the top. Questions? Open an issue on GitHub.