Jeff's comment about using Windows Azure Mobile Services is a great suggestion. Don't let the name mobile services fool you, It is setup for Windows 8 as well as iOS.
If you don't want to do that then you could always create your own service to connect to that to access the database. I do that with one of my apps, since I connect to it from iOS, android, WP7/8, Windows 8, and Facebook. I created a web service and connected to the database with EF.