As was stated previously in this thread
I have also used this solution to automatically turn on my nexus 7 once the tablet receives power.Quote:
I found a possible solution... You can change the bios settings to turn the tablet on whenever it sees power. I'll try it out sometime this week and report back.
EDIT: This worked perfectly. Unlock your bootloader and type "fastboot oem off-mode-charge 0". Now, even if the tablet is completely turned off, when you apply power it automatically boots to the home screen. No power button needed ever again.