What is a Deadman Switch?
In simplest terms, a deadman switch is a mechanism that is designed to stop operation of a machine, process or vehicle if the operator faints, falls asleep, dies, or is somehow incapacitated. The switch requires a constant pressure from the operator (either by foot or by hand) in order to keep the machine running.
It's most frequently used in trains or other dangerous machinery as a safety measure to prevent accidents if something happens to the operator. In transit trains for instance, if the operator faints, dies, etc., the train comes to a stop instead of continuing out of control.
Another form of a deadman switch is one in which you must perform an action (such as pushing a reset timer) at certain intervals. You don't need to keep continuous pressure as with a traditional deadman switch, but you do need to acknowledge at regular intervals that you want to keep the process (or machinery) operational. If not, the process stops, or changes how it functions.
Digital Deadman Switch
Last Landing uses the second form of a deadman switch, one in which you must perform an action (an acknowledgement) at certain intervals.
To get started, you create messages for your friends and family that hold information you want to disclose only in the event of your disappearance or death. When you perform a reset / acknowledgement action (via email or other mechanisms), you're telling our systems that you're okay and to keep your messages in an idle, unsent state.
When you create a message for a friend or family member, you establish how many days after your last successful acknowledgement that we should send the message. This in turn affects the intervals at which we send you reminders, and therefore the intervals in which you perform your acknowledgement actions.
If you don't perform an acknowledgement action within the timeframe you specify for a particular message, that message then gets sent. Otherwise, your messages continue in an idle, unsent state. Hence, the digital deadman switch.