Hertz-lite. is a free application that coaches you to stimulate your vagus nerve, reducing anxiety and putting you at ease.
It combines a breathing exercise with a gaze control exercise. A red dot sweeps a dial of ticks. As the dot passes over blue ticks, you breath in, as it passes red ticks you breath out. The speed of the dot is linked to your breathing, giving you feedback on your vagus nerve activation. The gaze control exercise builds focus and concentration.
Be aware that due to the screen-timeout limitations of the Apple Watch, you must occasionally nudge the Digital Crown to keep the screen alive! (To increase the screen display time, on your iPhone, in the Watch app, go to: My Watch (tab) > Display & Brightness > Wake Duration > On Tap "Wake for 70 Seconds". On the AW 6/7 you can set the screen to always on).