iCloud Sync is a Tier 1 feature that allows you to sync timers and their states across devices. Due to some timers being best left local, this feature is used at the Group level. You can create a new group that syncs to iCloud, and any timers within will also sync. Look for the iCloud icon to note which groups can sync.
To enable iCloud Sync globally, to to the Settings page and look for 'iCloud Sync', toggle it on. This should import any existing iCloud groups and timers once enabled. Simply toggle off to stop using sync on this device. Note: this means timers within iCloud sync groups will be deleted from this device (but will remain in the cloud)
When a timer is marked 'Self-Destruct' it will run to completion and notify you that the timer is finished. These alerts will repeat based on your timer's repeat settings until you stop the timer, at which point it will delete itself.
Templates are user-definable sets of intervals that can be as big or small as you need. They are handy when quickly creating, for example, a workout routine. You may have templates to represent a set of a given workout, including rest periods. You can append/prepend these templates to quickly build a complex routine on-demand, even from the watch or Shortcuts app! Included are a variety of default templates to give you some ideas of how to get started.
When a timer ends, the URL or Shortcut name will be opened to run any related actions. This can be especially useful if you want to create events that should be delayed by a timer. Once this timer completes, just tap the notification and the action will run.
When enabled, Critical Alerts allow Just Timers to override any silencing settings your device has enabled. This includes the mute/ringer switch, Focus Modes like Do Not Disturb, and even volume. This will act more similar to the native Timers app by overriding any settings that may cause you to miss your timer expiring.
Similar to the stock Timers app, the 'Stop Playback' feature (found under 'When Timer Ends' > 'Play Sound/Vibrate' when creating or editing a timer) will allow you to set a timer that will stop any media (music, video, podcast) that is playing. This is useful as a sort of "sleep timer", but do note: The app must be in the foreground for this feature to work, due to iOS limitations. The screen can be locked, but the app must be front instead of the Home Screen or another app when you lock it.
In Just Timers version 1 there were different limitations to Shortcuts than we have now. For the most part, x-callback-url is obsolete now, but I do have some new features added to v2. Unfortunately I don't have them all documented yet, so keep an eye on this page for an update. In the meantime, the documentation for v1 can be found here.
If you are dissatisfied with this app, please let us know first to see if we can help! If you're sure you want a refund, here are instructions for requesting a refund directly from Apple.