Rolla One

Rolla One is a health and fitness application that I built from the ground up through production release. It tracks activity in real time from connected devices and GPS, calculates workout metrics and visualises activity history.

Flutter Engineer at Rolla, responsible for the app from the first commit to production, including the native Bluetooth layer.

Workout data comes from several independent devices (a heart-rate wristband, treadmill and bike sensors) plus GPS. Each one has to be discovered, connected and kept alive during a workout, including in the background, and their raw data has to be combined into one coherent stream.

I designed the BLE communication layer in Kotlin and exposed it to Flutter through platform channels. It handles scanning and discovery, connection management, reconnect logic, background operation and state recovery. Raw sensor data is parsed into a unified real-time activity stream that the Flutter layer consumes.

• Native Kotlin BLE layer with reconnect logic and state recovery.
• Parsing of raw sensor data from multiple device types into one activity stream.
• Calorie and workout metric calculation from combined sensor and GPS data.

• Real-time activity tracking
• Heart-rate wristband, treadmill and bike sensor support
• Time-series charts for activity history
• Multilingual interface: English, Serbian and Russian

• Released to production and handed over as a stable, documented codebase.