How to make private Leaderboards for teams to compete in?

Hello,

Is it possible to have gamers 'make' their own leaderboards where only friends or teams can compete each other? So gamer x invites gamer y to join a certain leaderboard?

Maybe even a better combination with (international/home) leaderboard and a filter option to see score against friends or team/group available with one button, making it a private leaderboard?

Thinking about Soomla, but not sure if it can handle that. Not sure if Facebook SDK is what i am looking for or want to be independent on.

Does anyone have ideas, tips, links to App Store? Thanks for the help! Wouter