The app can vanish in the middle of a meditation. Almost by definition, people don’t use their phone while meditating. This means that iOS can yank the app out of memory because it’s apparently “not being used.” This is preventable if your app plays sound (such as a background sound or a narration), but the App Store guidelines are very strict in not allowing any of this trickery for apps that stay silent. We worked around this problem by scheduling a local push notification at the end of the meditation time: if all else fails, the user will still be notified when the meditation is over. There would be nothing worse than a meditation app that makes you wonder whether you’re done.
Looking at the Watch during meditation only shows the Watch face. While it’s possible to adjust the settings to show the current app, most users will only see the standard Watch face when they look at it while meditating. They’re not interested in the time, they want to know how far along they are.