Some enterprising iPhone users have discovered a security flaw in iOS 4.1, which allows you to make calls from locked iPhone. And
since the procedure itself is not too complicated, you might want to give it a try. On a locked iPhone, you need to press the "Emergency Call" button, but feel free to punch in any non-emergency number. The next step of a quick tap on "send" followed by your phone's lock key will put your device in the "phone" application mode. Voila!
Now, you are free to access all the features such as contacts, dial pad, favorites and voicemails. In the meantime, "home" button remains inactive. Again, when you reach the "contacts" tab, you can easily select a contact and send them emails and MMS. Eh, it's that simple!
Just recently, Motorola's BLUR had also caught the same bug, where you could use voice actions for making call from a locked screen. So, what are you waiting for! If you choose to give it a try, let us know how it worked out for you?
Source: BGR