Hi Thomas,
WiFi is only a network standard. It dosen’t matter whether you use WiFi or Ethernet port to connect the PIC controller to your Mobile, through a router.
You’ve to work on HTML, may be Javascript and learn how the communication happens between two devices connected in a network,
I hope you will find the following project helpful;
http://www.engineersgarage.com/contribution/remote-home-automation-using-gr-sakura