$ cat ~/case-studies/amber-alert-gps.md
Child-locator device companion
iOS + Android companion app for a child-locator GPS device. Real-time location, geofences, family sharing, and low-battery + SOS alerts.
Amber Alert GPS ships a hardware device children can wear; the companion app is the parent's window into it. The engineering bar is real-time, not feature-count — if location lags, the product has failed.
Backend is AWS IoT Core with Lambda processors and a DynamoDB hot table for the latest-known-location per device. Cognito for family identity, Pinpoint for push. We built the geofence logic server-side so kids can't work around it by killing the app.
SOS: a long-press on the hardware triggers a priority alert to every registered family member within 2 seconds of the satellite fix. That path is on a separate SQS queue with its own alarm if latency drifts.
- + kept: Server-side geofencing- cut: Client-enforced fence logic// why: A kid can't kill an app they don't control. Server-side was the only way.
- + kept: Separate SOS priority queue- cut: Unified notification pipeline// why: An SOS blocked behind a marketing push is a product failure. Isolate.
- + kept: Hot-table latest-known-location- cut: Full event-sourced history// why: Parents need "where is my kid now" in <2s. History moved to a cold table.
$ ready to start
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30 minutes. You leave with a scoped MVP plan, a fixed-price quote, and an AWS architecture sketch.