We develop mobile apps for children's GPS trackers that solve a real problem: a parent sees the child hasn't left school on time but the tracker's battery died. We ensure that a low-battery push notification arrives ahead of time, and the route history is accessible for any past day. This is not just a map — it's a safety system with geofences, an SOS button, and data privacy. Our experience includes more than 10 IoT and telematics projects, 5 years on the market. We guarantee compliance with App Store Review Guidelines and Google Play Policy.
Architecture: Device + Server + App
A children's GPS tracker is a watch, pendant, or small keychain with a SIM card. It does not run a mobile app. It sends SMS commands or GPRS packets to a server over a proprietary protocol. Popular models: Wonlex GW400S, WONLEX KT07, Smart Baby Watch Q90 — all use a simplified ASCII protocol over TCP or SMS.
The mobile app is the interface to the telematics server that already parsed the tracker's packets. The development challenge is creating a good UX on top of an existing or custom API.
How to Implement Map and Route History?
The current position of the child on the map is the top interface priority. A marker with the child's photo, last update time, battery level, and GSM signal strength. This is the first screen when opening the app.
History for the day — a track with stop markers. A stop is a cluster of points with speed < 3 km/h longer than 5 minutes. The address is reverse geocoded. "At school from 08:35 to 14:25, then at the mall from 14:38 to 15:02".
A timeline at the bottom of the screen — horizontal time scale with visit points. The user drags a slider — the map marker jumps to the position at the selected time. This is more convenient than scrolling through a list of addresses.
Safe Zones and School Schedules
Home geofence — a circular zone, the user sets a radius (e.g., 200 m). When the child leaves the zone — push to parents (both parents if both have the app).
School geofence — entering the zone at expected time: push "Vanya arrived at school at 08:42". This is called safe zone arrival/departure and it is the main feature parents want.
Schedule notifications. The parent sets: "Notify if the child hasn't arrived at school by 09:00". This is a scheduled check — a server-side task that at 09:00 checks if the child's point was inside the School zone in the last 30 minutes. Not an IoT event, but a scheduled check via cron.
SOS Button: What to Know?
The physical device has an SOS button. Child presses → tracker sends an emergency packet to the server → server pushes to all parents with an "SOS" label and current coordinates.
The push must arrive immediately with maximum priority. APNs critical alert (requires special entitlement from Apple) — arrives even in Do Not Disturb mode and vibrates twice. On Android — FCM priority: high with channelId: "emergency" with IMPORTANCE_HIGH and setBypassDnd(true).
Sound alert when the app screen is open — AVAudioPlayer (iOS) or SoundPool (Android) with the system alarm sound.
How to Protect Child Data in GPS Tracker?
The child's coordinates are data of a minor. Storage and processing require compliance with GDPR (Europe) or 152-FZ (Russia). Specific requirements:
- Encryption at rest (iOS Data Protection Class A, Android Keystore)
- Transmission only over TLS 1.3
- Access only by authorized parents/guardians
- Retention policy: location history max 90 days (configurable)
- Ability to export and delete data
In the App Store, such apps fall into the "Kids" category if explicitly positioned for children — then COPPA restrictions and limited advertising apply. If the app is for parents (not for children), it can go into the regular Navigation or Utilities category.
What Protocols Do Popular Kids Trackers Use?
Wonlex GW400S uses a GPRS-based protocol: short ASCII packets with coordinates, status, and commands. Position update interval — from 10 to 60 seconds. WONLEX KT07 supports SMS commands for configuration and call, with position sent every 5–15 minutes. Smart Baby Watch Q90 is a hybrid: GPRS for tracking and voice calls, SMS for SOS. We audit your tracker's protocol and implement the parsing.
Chat with the Child
A simple chat via server — text messages from parent to tracker (displayed on the screen), voice messages, or short predefined responses from the child. Limitation: the tracker's screen is small or absent — child's responses are often "button responses" (1 = OK, 2 = Coming home, 3 = SOS).
Implementation: WebSocket for real-time chat, push for new message notifications, MQTT from server to tracker for delivering SMS commands to the device.
Work Process and Timelines
| Stage | Content | Duration |
|---|---|---|
| Tracker audit | Device protocol, server API, supported features | 1-2 days |
| Map + history | Position, daily track, timeline | 2-3 weeks |
| Geofences and schedules | Home, school, scheduled checks | 1-2 weeks |
| SOS and notifications | Critical alerts, emergency pushes, sound | 1-2 weeks |
| Chat | Parent ↔ child messages | 1-2 weeks |
| Privacy compliance | GDPR/152-FZ audit and adjustments | 1-2 weeks |
| Publication | App Store + Google Play, code signing, provisioning | 1 week |
Checklist: Typical Tracker Integration Mistakes
- Protocol incompatibility: tracker sends data in HEX, server expects ASCII.
- Absence of heartbeat: if tracker does not send packets for >5 minutes, app loses connection.
- Ignoring timezone: coordinates come in UTC but are displayed without offset.
- Incorrect packet parsing: tracker may change field order in different firmware versions.
MVP (map + geofences + SOS + history): 6–10 weeks. Full platform with chat, schedules, audio, and compliance: 3–5 months. Cost is calculated individually after auditing the tracker's API and security requirements.
Our Strengths
Over 5 years of experience in IoT app development, 10+ projects for children's trackers. We guarantee compliance with app store policies and personal data legislation. Contact us — we will assess your project in 2 days. Get a consultation on tracker integration today.