A security hole in iPhone 4 software allows you to make a call after dialing a few pound signs and timing a few others as found by a MacForums member.
When your iPhone is locked with a passcode tap Emergency Call, then enter a non-emergency number such as ###. Next tap the call button and immediately hit the lock button. It should open up the Phone app where you can see all your contacts, call any number, etc.
A very similar security flaw discovered on the iPhone that we blogged about in 2008 that allowed people to easily bypass the lock screen to access mail, contacts and bookmarks. Apple later acknowledged the bug and issued a software update patching the issue.
An Apple spokeswoman’s response regarding the security flaw:
“We’re aware of this issue and we will deliver a fix to customers as part of the iOS 4.2 software update in November.”