Randomize the keyboard. Use a screen filter to reduce shoulder surfing. https://android.stackexchange.com/questions/27746/where-to-find-a-pin-lock-screen-that-

Randomize the keyboard. Use a screen filter to reduce shoulder surfing. https://android.stackexchange.com/questions/27746/where-to-find-a-pin-lock-screen-that-scrambles-the-keypad-on-every-use https://android.stackexchange.com/questions/27746/where-to-f...