Create a UI related for monitoring health or tracking various workout/training routines. It could be for a personal workout, for a team, or even gym equipment tracking customer workouts. Making a health app that is fun to use makes the entire experience more enjoyable and therefor more likely to be repeated.  

Tip: exercise regularly to get blood and oxygen flowing for health, better sleep, and to boost your creative mood. It's easier to be happy if you're healthy. :)

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NB: office/home exercise.