I think the best idea would be using a WebService to store and provide data.
So your solutions on differents plataforms and devices could just send requests to your WebService.
I would recomend the JSON instead XML for the requests, because JSON isn't heavy like XML and it has a SIMPLE SIMPLE formatting pattern.
By the way, if you don't want that your application have a networking need, you'll have to retrieve data and store on your devices/plataforms (and it could be a problem). So you'll have a work a little harder if two people modify the same data, think about:
Me -> Receive Data Person{Name=Felipe,Age=20} -> Modify Person{Name=FelipeMoraes,Age=20}
You -> Receive Data Person{Name=Felipe,Age=20} -> Modify Person{Name=FelipeUser,Age=20}
If you are working out with shared informations (informations that more than one person could edit) you could attend yourself about this, like locking the record or comparing the newest and the modifications (hard part, I guess).
Take a look about this integration architecture, it's simplified:

And take a look at some detailed articles:
http://www.themobilemontage.com/2012/11/29/successfully-integrating-web-services-into-your-android-apps/
http://code.tutsplus.com/tutorials/how-to-create-a-web-service-start-to-finish--net-22264