GPS-Based Ride-Sharing App Development

I need a skilled developer to create a ride-sharing application for both iOS and Android platforms, similar to Uber. The app should feature:

- GPS tracking system
- In-app payments
- User ratings and reviews
- Real-time notifications

Ideal skills and experience:
- Proven experience in developing ride-sharing or similar applications
- Strong knowledge of GPS integration
- Expertise in secure in-app payment systems
- Experience with user interface and experience design (UI/UX)
- Ability to implement real-time notification systems

Please provide a portfolio of relevant work and an estimated timeline for completion.