I can understand your project.
Main point is API integration of Strava , Nike + , Garmin and User account system.
I will build your project like this.
Laravel for Web System backend for managing account system and android and ios native platform for users.
My skill is
• Main Section: iOS & Windows Mobile
• Languages: Objective C , Swift , PHP, Java, SQL, HTML, CSS, JavaScript, C, C++, C#,
• Web Frameworks: Laravel , Wordpress , CodeIgniter, Zoomla
• Databases: Oracle, MySQL, MongoDB
• OS: Windows XP, Windows 7, Windows 8, Linux VCS/Centos, Git, TortoiseSVN, Mac OS
• BLE Device: iBeacon , Gimbal Beacon, Bluetooth 2.0 , 3.0
• Computer Graphics: OpenCV, OpenGL, DirectX