Access Manager for Android Tablets

The project is as follows: Platform: Android Tablets Objective: Completely revoke access to the Android system, showing a Login screen that will be used to regain access to the system. In detail: # Workflow # A timer has to be turned on. After this timer has reached a certain amount of time, say, 1h, the Android will be automatically blocked, only showing a Login screen and NOTHING else. From this login screen, the user will be able to input a passcode to regain access to the system for a certain amount of time, after which, the access will be revoked again, starting the process all over. Basically it's like this: [ 1 ] ---> [ 2 ] ---> [ 3 ] ^ | |----------------------| 1 - Timer is set. 2 - Timer has ended. Device was locked. 3 - Passcode was entered. Device was unlocked, setting a new timer (1). # Plus # I must be able to remotely block and unblock this Android tablet by sending it a message online. As for the pass codes, I also need a way to generate pass codes and have the Android tablets verify the valid codes to give back access to the tablet.