the Fitbit mobile app
A simple design analog clock where balls orbit to represent analog hours and minutes. An additional animated small ball is there for seconds.
Everything turn around a label displaying the current heart rate, this label is pulsing on every 2 seconds, reminding the user the role of this value.
The fun thing is that the orbits are displayed according to your wrist orientation and your movements (walk, jump,...) thanks to accelerometer data.
Note that the sensors used in this clockface are turned off when the clock is not displayed.