Microsoft's limited access to the GamerTag/Gamercard XML feed is the barrier of entry. I've looked into building a similar app but still awaiting MS approval. A

Microsoft's limited access to the GamerTag/Gamercard XML feed is the barrier of entry. I've looked into building a similar app but still awaiting MS approval. Although there is an application to gain direct access to the feed, I suspect it is mostly limited to developers who are already part of the network (ie. a paying member of the Xbox Registered Developer Program).