Cross-Platform Booking App Development

I need a mobile app built for both iOS and Android platforms. The primary purpose of the app is for bookings, like a car parking app, or library lockers. Something a user can access with a pin code, or bar code on their phone.

Key Requirements:
- User-friendly interface
- Secure payment integration
- Real-time availability updates
- User account management
- Push notifications for bookings and updates

Ideal Skills and Experience:
- Proven experience in mobile app development
- Expertise in both iOS and Android platforms
- Strong UI/UX design skills
- Experience with secure payment gateways
- Background in developing booking or similar apps

Please provide a portfolio with relevant work. Looking forward to your bids!