Mobile Health Data Sync: Multi-Device Deduplication

Devices Streaming Steps

Reconciliation Algorithm

Merge window Δt 1.2 s

Priority source (wins a conflict)

Emission rate 1.0×

Live Readouts

Raw total (naive sum)

Resolved total

Double-count error

0.0%

Events merged

Events accepted

Accepted — counted once

Merged — same steps, discarded

How it works

Real mobile-health apps aggregate steps from several APIs at once (Apple HealthKit, Google Fit) that each proxy a different physical sensor — phone accelerometer, watch, fitness band. Worn together, the same footstep gets reported two or three times a few hundred milliseconds apart, with different timestamps and step counts.

for each incoming event e = (source s, time t, steps v):
  raw_total += v                      // naive HealthKit-style sum

  prior = most recent ACCEPTED event
  if prior exists and |t - prior.t| < Δt:
      // same physical burst — reconcile, don't double-add
      winner = higher-priority(s, prior.source)
      if winner == s: prior.value = v   // replace with the trusted source
      merged_count += 1
  else:
      resolved_total += v
      accepted_count += 1
      prior = e

error% = (raw_total − resolved_total) / resolved_total × 100

Merge window Δt — how close in time two devices' reports must land to be treated as the same footsteps rather than independent steps. Too small and real double-counting slips through as "new" steps; too large and genuinely separate activity bursts get discarded.
Priority source — which sensor's step count is trusted when two devices disagree about the same burst (e.g. a watch's accelerometer is usually more accurate than a phone left in a bag).
Devices on/off — toggling a source stops its stream; with only one device active there is nothing to reconcile and the error stays near 0%.

Green pulses are steps the aggregator kept once; red pulses are duplicate reports of steps already counted, discarded by the merge-window check above before they ever reach the resolved total shown on the Health Record hub.

Phone Watch Band

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