Apple has a Patent for Slide to unlock. Now Google has a patent for pattern unlock. Good luck seeing either on a Blackberry as standard. I'm surprised Apple hasn't tried sueing the app makers.
well if all you want is a screenlock you can settle for the one that appears on your playbook when you are bridged and are out of blu tooth range. doesn't do much in terms of actual protection as it automatically "unlocks" as soon as you come within range of your phone but it serves as a deterant for wondering eyes in case you step away from your playbook.