Develop mobile app for all platform.

I want to develop a mobile app with connected database. It must work on iphone, windows and android. Therefore must use a tool that make it easy to deploy on all platforms. Also pc and mac shall worke fine. It main feature is to use push technology to publish image, text and video to user. Shall notify user when he gets a new message, same like whatsup, or viber. Admin area where i can sent and orgranize different category and topics. When user install the app, he will be able to read and see all information i sent to him. Idea is to have platform to publish the information to those who want to see it. Other features will be discuss