How to unlock apple iPad without a computer

If it's only locked and not disabled you might (if you had Find iPad enabled on it and the iPad is online) be able to send a remote wipe message to it from Find iPhone app on another iOS device or http://www.icloud.com on a non-iOS device or computer. If it's disabled you will have to connect it to a computer's iTunes in order to reset it.

See : If you forgot the passcode for your iPhone, iPad, or iPod touch, or your device is disabled - Apple Support