Android App with SIP, XMPP & REST

I'm seeking a developer to create an Android app that supports rich communication features including voice calls, text messaging, and video calls. The app needs to be optimized for smartphones.
Key Features:
- Use of PJSIP for the voice call feature
- Integration of SIP and XMPP for seamless communication
- Use of REST APIs for text messaging

Ideal Skills:
- Proficiency in Android development
- Experience with SIP, XMPP, and REST APIs
- Knowledge of PJSIP integration
- Understanding of smartphone optimization
- Experience with UI/UX design from reference material

Duration:
- The project duration is 3 - 4 months

This project requires a developer who can deliver a high-quality, fully functional communication app. Please include examples of similar work in your proposal.