A free program for Android, by Best zipper lock screens.

You can use Cute Zip Screen Locker to create a unique and personalized screen locker for your phone. The app offers an in-depth personalization option where you can change all of the following:

• Choose your wallpaper for the locker screen and device background.
• Choose the animation speed for the zipper to unfold instantly or just a bit slower.
• Choose whether you want to hear the zipper sound and the vibration.
• Turn all the widget options off or on.
• Set a password before unzipping the screen.
• Display the Date, Time, and battery level.

With this, you can ensuring that nobody can access your phone without the correct password.