How Pelion Posture works

Calibration, local feedback and the MCP boundary

Camera pixels stop before the optional MCP boundary

The diagram separates the app's visual input from the derived numbers that can be written locally. It also separates visible product feedback from MCP: ordinary posture monitoring does not require MCP, and MCP is off by default.

What Pelion measures—and what the number means

Pelion observes a camera-derived angle relative to the upright posture you calibrated. It then interpolates a load estimate from the angle values published by Hansraj (2014). The angle is an observation; the load is a model output. Neither tells Pelion why you are in that position or whether it causes pain.

See the interactive neck-load model and its research limitations. If you have persistent pain, weakness, numbness, balance changes or another worrying symptom, use appropriate clinical care rather than a posture app to investigate it.

Measured on the current public build

Download the complete normalized JSON dataset or CSV table. The fixed protocol SHA-256 is 22db7d94578f8eaeac684eeeeaa1f2861592a850cdf7d4cbb66efb806c467da1. All failures would remain in the result; there were none.

What an MCP client can—and cannot—read

MCP is disabled until you turn it on. When enabled, the app rewrites one private local snapshot at most once a second. The bundled server reads that derived snapshot and responds to the client process over stdio. It does not receive a camera buffer.

{
  "state": "watch",
  "neck_load_kg": 15.2,
  "neck_load_display": "15 kg",
  "forward_tilt_deg": 23,
  "confidence": 0.94,
  "updated_at": "<synthetic timestamp>"
}

Use the MCP setup guide and complete resource/tool contract for client configuration and availability details.

What this page demonstrates—and what it does not

Video transcript

1. How Pelion Posture works. All-day monitoring is free, and camera processing stays on your Mac.
2. First, sit upright for ten seconds. That becomes your baseline, not a textbook-perfect spine.
3. Pelion monitors locally and shows a relative estimated neck load. It cannot diagnose pain or injury.
4. Moving forward changes the estimate; returning upright lowers it. These example values are synthetic.
5. Camera images stop before MCP. Only derived posture can cross the optional local-agent boundary.
6. MCP is off by default, uses standard input and output, and opens no listening port. This public MCP binary is Apple-Silicon-only.
7. An agent can read derived numbers, not pixels. This is a controlled synthetic response.
8. A tuning request waits for approval in the app. It is not silently applied, and Pro agent tools are not open yet.
9. On one M5 Mac across five runs, the current snapshot read median was 0.761 milliseconds, with a 0.672 to 2.497 millisecond range. Process start to initialize had a 16.2 millisecond median and a 16.1 to 855.3 millisecond range. These local timings do not generalize to every machine.