In Android Customize your lock screen

          

            Android gives you a few solid options for keeping other people from getting access to your phone. Of course, there's the trusty four-digit PIN. But you can also set up a regular password like you'd use on your computer. Or you can get into your phone by dragging your finger to connect a series of dots in a unique shape. If you're running Ice Cream Sandwich, you can also give "Face Unlock" a try. Your phone will use its front camera to detect who's holding the phone, unlocking only for the real owner. This isn't a particularly secure option (it can be defeated using a picture of the owner, for example), but it's a lot of fun to show off. (If you're running Froyo or Gingerbread, the free Visidon AppLock can do the same thing for your messaging and email apps.)
          If you're less worried about security and just want a simple slide, you also have the option to quickly access the camera from the lock screen. Just slide the lock to the left over the camera icon. And if you want to trick out your lock screen even further, you can use WidgetLocker's LockScreen app ($2.99) to get music controls and customized sliders for particular apps.