Superfeedr is an API which will help you gather data from feeds that you're supposed to curate yourself. So the whole process starts with you collecting a list of feeds to which you want to subscribe.
The Track API does not help you find feeds, but rather helps you build virtual feeds that match a given criteria. For example, if you want any mention ot 'stackoerflow' in any feed, you could use track for that. Think of it as RSS feeds for search results, but in realtime (forward looking).
Finally, if you use XMPP, you don't need a callback url, as these are part of the PubSubHubbub API.