Never lose anyone in the crowd.

Not everyone — alert fatigue kills response time. The cascade is layered: the lead's phone fires first (push + sound, named pupil), co-leads get a silent secondary notification ~10 seconds later, and ops back at base see it on the dashboard as a logged event. Parents only hear about it if the lead presses "escalate" — never automatically. Other children's bands stay silent; only the wearer who actually strayed gets a vibrate to stop walking.

Three connectivity tiers. Primary is sub-GHz mesh between bands — 500m peer-to-peer, no SIM needed. Secondary is Bluetooth from one "gateway" band to the lead's phone for cellular relay. Tertiary is an embedded NB-IoT SIM on the gateway band itself — low-power roaming (~£0.50/month per group), pings position every 60 seconds even in true wilderness. Together that covers 99%+ of UK trips, including Snowdonia, Scottish Highlands and the Lake District.

Audit-aligned, not yet certified — and that's a deliberate position at pilot stage. The product already produces every artifact a DfE, CQC or Martyn's Law audit needs: supervision logs, headcount records, incident timelines, opt-in consent. The remaining steps — DPIA, UKCA self-declaration, ICO consultation — are £15K and three months of work, all included in the pilot funding line and closed by month 3. Trip data is owned by the school or operator (clean GDPR processor/controller split), auto-purges at 90 days, and nothing is sold or shared with third parties.