WARNING THIS WAS BUILT AS A JOKE APP, JUST BECAUSE IT COULD BE DONE. PLEASE READ AND DON'T USE MALICIOUSLY
What It Is
Okay well while building Portal (https://market.android.com/details?id=com.gflam.portal) I had an idea that I could use these new windows which everyone is going crazy over to just completely cover the screen and make the phone unusable. I took it a step further and added a boot receiver so that it would start up as well after rebooting. What this app does is pictured below. Essentially it just covers your entire screen with a brick image. Yes the status bar still shows I didn't take that much time to explore covering that but the thing is even if you pull the status bar down and click something in it whatever opens will still show behind the brick wall so it still renders the phone useless.
Well first because I could and second thought it might make for a good joke to prank friends and watch them sweat a little. Again I can't stress this enough don't use it maliciously it was intended only for joking reasons
Getting Rid Of It (Both Commands Require Root)
To the best of my knowledge getting rid of it requires a computer with adb set up, although if you reboot you will most likely have enough time to beat the boot receiver to uninstall it but this also depends on how many apps you have running at boot. Anyway to get rid of it no matter what you can use either of the following commands in adb shell. The first one will completely uninstall it and the second one will just kill the app but keep it installed so you can run it again if you want.
adb shell uninstall com.gflam.brick
adb shell killall com.gflam.brick
Downloading (See Link Below)
Again please make sure you know how to get rid of it use at your own risk and don't use maliciously.