BurnIn

"Drag To Unlock" screen. Text is "Drag To Unlock" and "Shut Down"

After "Drag To Unlock" screen, when you "Drag To Unlock", you get this screen. In order, "Start Burnin", "Reset Test Enviroment", and "Quit"

???

Burnin is codename for the (supposed) diagnostics tool used when iPhones are sent in to Apple for repair. Unfortunately, not much is known about this mysterious

UPDATE - An anonymous source has informed me that this is how it works. Apple restores a special firmware to the iPhone, but it is based of a regular firmware. At boot, /AppleInternal/Applications/SwitchBoard/BurnIn.app/BurnIn will run. It checks /AppleInternal/Diags/purpleskank/config.plist for configuration information, such as version (1.3.0 in this case), where to store the logs (/Library/Logs/BurnIn/ in this case), what level to set the backlight to, and also, some kind of cleanup script is defined (/AppleInternal/Diags/Utilities/burnin_cleanup.sh). What it actually does is still not known though. Two log files are also left by it, by doing whatever is done :P They are /Library/Logs/BurnIn/burning_log.xml and /Library/Logs/BurnIn/burnin_log.txt.