My VirZOOM Challenges
The Challenge page allows you to challenge friends to timed matches on any game level. When challenge members play a game, it gets recorded on a local challenge leaderboard they can all see, and results go on their activity log. Choose a game level, time period, "best" or "cumulative" score, and which friends to play.
Challenges are also great for head-to-head events, in games like Racecar Live and Tank and Pegasus Gem Hunt, because members will only see other challenge members during the event.