Mythbusters - Busted
Mythbusters recently did a segment on their show testing thsi 'Myth'. They tested if a .45 round could be stopped by a mobile phone.
After some testing on the range, this was 100% 'BUSTED'.
The only way i could see how a phone could stop a .45 round was if it was fired from a LONG ways a way and had lost most of its energy BEFORE hitting the phone.