There are plenty of ways to unlock a secured phone, the most common being a four digit password. Google Android has the option to allow you to draw a pattern onscreen. This is a lot more intuitive than typing a four digit code and can be done with one hand even without looking at the screen of the phone.
This is apparently more secure than anyone thought. The Verge reports that the Federal Bureau of Investigation had to unlock a Google Android phone in connection with an investigation. Unable to break the code, they had to file a warrant to get Google to help them unlock it.