The problem is not with writing an app like that - it is not that hard. The problem is with getting content for it. This info (especially real time data) is a pretty hot marketable commodity and aside from doing screen scraping it is not easily available. For example, MLB posts real time data in XML format to their server which anyone can access but using it for any distributed application (free or not) is a violation of their terms of use:
http://gd2.mlb.com/components/copyright.txt
So whoever writes this app needs to talk to them about licensing and access fees and all the other legal jazz. If content would be available for free (or a small reasonable fee) then writing a parser application would be pretty straight forward.