One of the nice keypad screen lock application in android market.
For increased security change your password for the first time,
How it works:
You have to just enable lock screen in settings in this application and whenever you unlocks your phone, you will be passed through this keypad lock.
This is a new way to lock your phone, in no way your phone will get locked permanently.
In case you forgot your password, you can just press home button and you will come back to main phone screen and unlocked too.
No data will be deleted using this application.
Few customizations you will find in the settings page, like sound on or off and vibration on or off. It gives some look and feel of iPhone lock screen but this is completely different.
Download and enjoy.