Cross-Platform Productivity App Development

I'm looking for an experienced app developer to create a productivity app focused on task management. The app needs to be developed for both iOS and Android platforms.

Key requirements:
- Task management as the main feature
- Intuitive and user-friendly interface
- Secure and efficient data storage
- Synchronization across devices

Ideal Skills and Experience:
- Proven experience in developing cross-platform apps
- Expertise in task management features
- Strong UI/UX design skills
- Familiarity with data security protocols

Please provide examples of previous work and a timeline for completion.