Project Description: I am looking for an experienced Flutter developer to build a PPG (Photoplethysmography) mobile application. I already have a fully functional web-based version (Javascript/Browser) that captures pulse and stress levels via the webcam. I need this ported to a native Flutter app to achieve medical-grade accuracy using better hardware control. The Goal: Turn the phone’s camera and flashlight into a sensor to measure: Heart Rate (BPM) HRV (Heart Rate Variability - SDNN) Stress Index based on RR-Intervals. Key Deliverables: Camera Sensor Module: Implement the Flutter camera package to stream raw image data. Crucial: Must handle "Torch Mode" (Flashlight ON) and Lock Exposure/White Balance to prevent signal noise. Extract real-time luminance (brightness) data from the YUV/BGRA image stream. Signal Processing & Math: Convert raw brightness data into a clean waveform (Peak Detection). Calculate BPM and HRV/Stress in real-time. Note: I will provide the logic/formulas currently used in the web app. API Integration: Post calculated session data (Pulse, SDNN, Stress) to my existing REST API (pulse_stress table). Biofeedback Module: A "Therapy" screen that plays specific Audio/Video content. The content must react dynamically to the user's real-time Stress level (e.g., changing visuals if stress drops). Resources Provided: Access to the existing Web App for reference. All mathematical formulas for HRV and Stress calculation. API Endpoints. Ideal Candidate: Strong experience with Flutter CameraImage streams and Isolates (for performance). Understanding of basic signal processing (filtering noise from data). Experience with real-time charting (e.g., fl_chart).