MoonScore is a small, lightweight, webservice that keeps track of highscores on many different games.
It's currently in the later stages of development, but the release date is still TBD.
I'll be releasing the service itself for free, though I will be charging a small amount for the Unity plug-in that will be up on the asset store on release.
Keep an eye out for updates over on my twitter feed and on here. Also keep an eye out over at getmoonscore.co.uk for the documentation.