Add Challenge Matches (quick head-to-head match-ups)
Easily challenge another player to a best-of-X challenge. Match Play would let you send a challenge to a another player. That person would accept the challenge and Match Play would walk you through the challenge game by game.
Results would be stored for each individual game and you'd be able to get an overview of results over time along with any other stats that can be thought up.
John Delzoppo commented
Have you considered implementing the option to enter the machine name for each game of the challenge match? It would give more reason to look back over old challenges if the machines were listed rather than game number 1, 2, etc.