You can set a password on your PlayBook tablet, so anyone try to unlock and use it then have to enter password first. Lets see how to set password on PlayBook Tablet.
Set password on PlayBook tablet
Tap on “Security” menu on the left side and then tap the “Password”
Tap the ON/OFF button to enable password
Enter the password and re-enter to confirm it, when done tap the “OK” button
You can also set the “Lock After” time, tap on Minutes drop down and select one.