I feel like this is almost certainly a duplicate, but I couldn't find what it's a duplicate of.
Is there an RSS feed for updates (new answers, edits, comments, maybe even votes) on your "favorite" questions? If no, can we have one?
This is now possible. I have written a small application called Stack2RSS that does exactly that.
Here is how it works: given an API request, the app will convert it to an RSS feed. Since there happens to be an API method for retrieving a user's favorite questions, stack2rss can easily generate a feed for this.
An example that fetches Jeff Atwood's (user #1) favorite questions on StackOverflow: