1. A system configured to detect an event while the system is powered off, the system comprising: an input that is configured to receive an electrical signal created by an event, even while the system is powered off, a zero-power event memory configured to: operate in a first state that indicates no event has occurred; operate in a second state that indicates an event occurred; and use the electrical signal created by the event to switch from the first state to the second state, thereby storing an indication that the event occurred; and a read subsystem that is configured to, when the system powers on, access the zero-power event memory and determine whether or not an event occurred while the system was powered off.