You will be sent a text notification informing you of the contact who has opted-out (e.g. replied "stop" to one of our notifications).
Should this contact be your only "active" contact, your check-ins will be disabled until the contact opts in or you add another active contact. Instructions will be sent to you on how to relay information to your contact explaining how they can opt-in again. This process is simple, the contact only has to respond with the word "unstop".