It doesn't matter very much how awesome your device is. You need at least a second person who would also get the alert as a backup (assuming this is a critical system that you really care about, otherwise you wouldn't want to be on-call for it in the first place).

As the primary responder, your responsibility is to acknowledge any alert within a minute or so. Otherwise, the backup person would have to jump in.

To ensure "accountability," you may have a manager who would be a third backup and can escalate up from there.