I understand all thing you told me except this;
Do you have to write an Android app? If you need to have a web interface for the people outside of the city, then why not just use that same interface with a the Arduino's browser?
Yes, there suppose to be android app. With computer control part i can use arduino's browser. But with phone control part i have to create a basic android app. I think if i hook up my android app and Arduino's browser, my problem will be solved. If it is not possible, i need to create 1 for computer and 1 for phone?
And I decided to buy this equipments => 'Arduino UNO R3' and 'Arduino Ethernet Shield Rev3 WITH PoE Module'.
I really look forward to start coding if i understand this last problem...