I am seeking a skilled React Native developer to build a Minimum Viable Product (MVP) for a mobile app that will track and analyze how Brazilian Jiu-Jitsu athletes train. This app will connect to a custom wearable IMU sensor to provide athletes with objective, data-driven insights into their performance.
You will be responsible for building the first version of the app for both iOS and Android using React Native. The core function of the app is to connect via Bluetooth Low Energy (BLE) to the IMU sensor, process its data into five key performance indicators, and display them in a simple, functional user interface. For this MVP, I want to prioritize core functionality and data accuracy over complex visual design. This does NOT need a nice UI.
Core MVP Features:
The app will have a simple 3-tab navigation structure:
Tab 1: Daily Dashboard
Display five consolidated metrics from the user's most recent training session:
Work Rate Score
Daily Impact Load
Positional Dominance Score
Performance Decay (%)
Takedown Quality Score (/100)
Tab 2: Performance Trends
Display charts showing the user's average for the same five metrics over a 7-day and a 30-day period.
Tab 3: Record & Tagging Station
Record Match: A feature to initiate video recording using the phone's camera while simultaneously starting a data-logging session with the IMU sensor.
"In-App Lite" Tagging: A simple interface where users can watch their recorded video and tap event buttons (e.g., [Takedown], [Sweep]). Your code must capture the timestamp of the tap and use an algorithm to link it to the nearest significant event in the sensor's data stream.
Technical Requirements & Specifications:
Platform: React Native for cross-platform support on both iOS and Android.
Hardware Integration: The app will connect via Bluetooth Low Energy (BLE) to a custom IMU sensor based on the STMicroelectronics LSM6DSV320X. This is a mandatory requirement.
Data Processing: The developer will be responsible for implementing the algorithms to calculate the five consolidated scores. The BJJ-specific logic, rules, and weighting for these formulas will be provided by me.
Data Storage (Local-First MVP): For this initial version, all user data (metrics, tagged events, videos, and demographic info) must be stored locally on the user's device. No cloud backend or user account system is required at this stage.
User Profile (Local): The app must have a simple, local-only profile screen where users can input their demographic information (Sex, Belt Rank, Age, Training Frequency, Weight). This data will be saved on the device for future use.
Future-Proof Design (Critical):
Hardware Abstraction Layer (HAL): The app's communication layer must be architected to be independent of the sensor hardware, allowing for different hardware to be used in the future without a full rebuild.
Scalable Architecture: The app must be designed with the future in mind. I plan to add user accounts, a cloud backend for data synchronization, and AI-driven workout suggestions in Version 2.0. The MVP's architecture must be modular to support these future features without requiring a complete rewrite.
What I'll Provide:
Clear product requirements and user stories.
The detailed logic and weighting for the custom metric formulas.
A fully functional prototype of the IMU sensor hardware for development and testing, which will be shipped to you (if needed)
What I'm Looking For in a Developer:
Proven experience building and deploying production apps with React Native.
Demonstrable experience working with Bluetooth Low Energy (BLE) is essential. Please provide specific examples of previous BLE projects.
Experience with IMU sensor data, data visualization, and/or sports analytics apps is a strong plus.
Experience in Brazilian Jiu Jitsu or Wrestling is a PLUS
A strong understanding of mobile app architecture for scalability and future-proofing.
Excellent communication skills and the ability to work with a non-technical product owner.
COMPLETE SPOKEN fluency in English to properly convey updates and answer questions
How to Apply:
Please include the following in your proposal:
A brief summary of your React Native and BLE experience as it relates to this job posting
Your proposed technical approach for building this MVP, specifically addressing the local-first storage and the architecture for future scalability.
A ballpark estimate for the project's cost and timeline.
Links to relevant apps in the App Store / Google Play you have built.
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