I posted the above back in Thread #9, and since GBC allegedly declared the existence of this App in his April 20th SMS to Allison it could become an interesting piece of evidence.
As CaseClosed pointed out, location (GPS) services can be switched off manually which would disable the App on the iPhone. Or the phone itself could be switched off to disable the App.
Another poster also pointed out that a phone, even when switched off, can still be pinged and triangulated from mobile phone towers. It seems this was the case for Allison's phone (though we don't know if it was switched off) which indicates it wasn't destroyed.
My guess is that GBC probably divulged the April 20 SMSes to Allison to police on the morning of the search for her, knowing that the search for it using the App would be fruitless because he had either disabled location services or switched her phone off. It would then be imperative for QPS to find Allison's phone to check WHAT TIME it had been switched off. Usage statistics should record this.
Further, if GBC was in the habit of using the Find My iPhone App to locate Allison, it could weaken a defense argument that her phone might have been wrenched from her hands during an altercation with an attacker/abductor during her walk and tossed into the scrub nearby. In this scenario, one would have to presume the attacker had some clue as to how to turn the phone off, and to stop and take the time to do this.
MOO