Ex. bluetooth sketch for android to arduino

Hi all,

Looking for an example sketch that would help me have an arduino LED light up when you receive a phone call through bluetooth protocol. I am sure it has been done before but not sure what is the best app to use on an android/iphone device. Basically something really simple as in the phone sending a "1" when there is a phone call. Then a "0" when the phone call has ended.

Idea is eventually adding another class in the code for when you receive a text, etc. Any guidance or help would be greatly appreciated! :)