Aren't there already rss feed plugin's for the platforms you already mentioned?
I know there is one for Wordpress, I used it to bring news feeds from other sites to mine, though I stopped as it was pulling too much content I really had no interest in. (Mac Rumors feed for a Walking and picture taking site? Ya, not really on topic 🙂
I guess what I am saying, is either your offering money for code that has already been developed (recreating the wheel) and wasting money, or you need to research the platforms individually, find the ones that do not have an RSS feed, and offer money to develop those.
Thats my 2 cents.