General:
* Distraction
* Amusement
* Entertainment
* Recreation
* Pastime
* Hobby
* De-stressor
More specific:
* Redirection: When referring to changing the course of something.
* Detour: When referring to a change in direction, especially in travel.
* Distraction: When referring to something that takes your attention away from something else.
* Escape: When referring to something that provides a break from reality.
* Diversionary tactic: When referring to something used to mislead or confuse an opponent.
The best synonym to use will depend on the specific situation and what you are trying to convey.