IoT Developer — Sensor Monitoring Dashboard App with Real-Time Alerts

We need a developer to build a mobile app that monitors data from IoT sensors and alerts us when readings go outside safe limits. What we're monitoring: We have sensors measuring temperature and humidity (open to your recommendation on hardware/protocol) and need an app that reads this data live and warns us before something becomes a problem. What the app needs to do: Display live sensor readings on a simple, clear dashboard Show history/trends over time (last 24 hours, 7 days) as charts Send push notifications when a reading crosses a set threshold (too high / too low) Let us set and adjust those threshold limits ourselves in the app Handle a sensor going offline gracefully (alert us that it's offline, not show fake zeros) Support multiple sensors/locations Tech preference (open to recommendations): Cross-platform app (iOS + Android) MQTT or a cloud IoT backend of your recommendation Push notifications What we're looking for: Real experience with IoT sensor data and real-time dashboards (please share examples) Strong at handling timeseries data, thresholds, and reliable alerting Clean, documented, maintainable code To apply, please include: Examples of IoT/sensor or dashboard apps you've built Your recommended approach for the alerting and threshold logic Estimated timeline and cost for a first working version