Arduino make Skype call on my android phone

Dear members,

I want to make this project, whose idea is :

I've arduino board and sensors placed at my home gate, and also place an android smartphone.

Scenario is, whenever someone ring my home bell, then that Android smartphone automatically makes a Skype video call.
And I can able to see and talk to that guest from all over the world.

Thank you,
Your comments and helps are appreciated.
Please tell me which hardware or circuit i have to use.