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2.0.26London / Remote
← The workExperiment · an on-device experiment

A private live coach for video calls

A real-time call coach that runs on your laptop

A Mac app that sits around the notch and coaches you live during a video call — surfacing your talking points, flagging when you're talking too much, reading the room — without sending anything off your machine.

Cloud transcription, lag, and a privacy problem → a private live coach that runs on your own laptop.

On-device LLMsSwiftScreenCaptureKitmacOS
BeforeAfter
Where the AI runsin the cloud, on a serverentirely on your own laptop
Speedlag that breaks 'real-time'fast enough to coach you live
Ongoing costa per-minute charge for every callnone — it runs on hardware you already own
Privacya private call streamed to a servernothing leaves the device
Setupper-app integrations and audio pluginsone app, using the system's own recording path
The delta

Running the models locally turns an infeasible product into a feasible one. The blocker was never the idea — it was lag, cost, and privacy, and on-device AI dissolves all three at once. This is a whole product category that only became possible in the last generation of AI models. The work here was proving that, rigorously, before anyone wrote production code.

What I built

A serious Stage-1 feasibility study — not a finished product, but a rigorous go/no-go on whether a real-time call coach can actually exist. Three things all have to be true for it to work, and the study tested each one honestly:

  • Can it run on the device? The technical core is a small Mac app that sits around the notch, wakes up on its own when you enter a call (with no per-app integrations), and captures both your audio and the other person's through the operating system's own screen-recording path — deliberately avoiding the audio plugins that make setup painful and scare people off.
  • Do the costs work? Running the AI locally means there's no per-minute charge for every call, which is what makes the economics hold up at all.
  • Is getting started effortless? Every permission the app needs was mapped in the exact order a new user would hit it, because each extra permission request roughly halves how many people finish setup.

Once running, the coach surfaces your prepared talking points, flags when you're dominating the conversation, and offers a read on the other side's mood — all live, all on the machine.

Why it matters

The benefit is a private coach that helps you in the moment, on calls that genuinely matter — and the reason it can exist at all is that the AI runs on your own laptop. In the cloud, real-time call coaching is a non-starter: the lag breaks the "real-time" promise, the per-minute cost breaks the economics, and streaming a private conversation to a server breaks trust. Run the same intelligence locally and all three objections disappear at once.

That's the point of the study. It's a clear example of a product the previous generation of AI simply could not support, and this one can — and the valuable work was proving that rigorously, so anyone building it knows it's real before they spend a dollar on production.

How it works
  1. 01
    Run

    The app sits quietly around the laptop's notch, ready and out of the way.

  2. 02
    Wake

    It activates on its own the moment you join a video call, with no per-app setup.

  3. 03
    Listen

    It captures both your audio and the other person's through the operating system's own screen-recording path, avoiding fragile audio plugins.

  4. 04
    Coach

    It surfaces your prepared talking points, flags when you're talking too much, and offers a read on the other side's mood — live, on the machine.

  5. 05
    Protect

    Everything happens locally, so nothing about the call is ever sent off the device.

The bottom line

This is a clean example of a product the previous generation of AI simply could not support, and this one can. The deliverable was the honest feasibility call — proving the idea is real, and showing exactly why on-device AI is what makes it possible.