Provided, inter alia, is a system for generating substantially simultaneous alerts, in which a plurality of user devices is accessible via at least one publicly available network. Each such user device has installed on it an alert-based client. A server is configured to download identical alert information, including a message that has been encrypted, to the plurality of user devices. The alert-based clients are configured to receive the alert information and, in response: (i) to store the message in encrypted form until just prior to a specified delivery time; and (ii) to decrypt and deliver the message substantially at the specified delivery time. By virtue of the foregoing arrangement, substantially simultaneous delivery of the message to the user devices is achieved.