What is a live activity?
A live activity is a small readout of something that is happening right now and changes over time, such as a countdown, a delivery or a song. Apple’s design guidance says a Live Activity lets people track the progress of an activity, event or task at a glance, for example the time left until a food delivery arrives.
Where Apple shows them
Apple lists these places for Live Activities: the Lock Screen, the Home Screen, the Dynamic Island and StandBy on iPhone, and the menu bar on a Mac.
Why it matters for notch apps
In notch app marketing, the word means a tiny readout that stays visible while the panel is closed, instead of making you open the panel to look. Whether you want that is a real choice. A readout at the edge of the screen can help you keep an eye on a timer, and it can also be one more thing moving in your view. Each notch app builds its own version, so ask whether the readout stays when you move the pointer away, and whether it needs the panel open. The guide on the Dynamic Island for Mac has a table of what to check with a trial.
NotchStar
NotchStar describes itself as a toolbox you open on purpose. Its Timers tool keeps counting while the notch is closed, and it plays your chosen sound when the time is up.
Related
See Dynamic Island for Mac and the definition of a notch app.