Can you just break the glass and open the lock?

Yes, you can. The Ultimate Lock was built as a tool to protect you and your family; and give you the time needed to get to a safe room and contact authorities to help you. However, the sound of the breaking glass is very loud and distinct. Upon hearing the sound of breaking glass, and seeing the intruder trying to open the lock, this shortens his chance of survival, and therefore giving you ample time to call the authorities.