here's the video demonstration: http://youtu.be/3Zcdc33xbFQ
using this script on your UI gameobjects you can detect clicks and double clicks using conditionals. create a variable of type Btn and use it in an if statement. eg:
Btn fireBtn;
void Start(){ fireBtn = GameObject.Find("Fire Button").GetComponent(); }
void Update(){
if(fireBtn.Clicked)
Debug.Log("bang")
if(fireBtn.DoubleClicked)
Debug.Log("bang bang")
}