This is something I have a real need for. Specifically, podcast hosts. I want to follow certain hosts and listen to every random show they're on.
Some hosts do keep lists of their appearances across many shows: http://hypercritical.co/about/appearances/
But that forces me to manually find the episodes and add each one to my podcast app.
I want something that aggregates appearances into a cross-podcast RSS feed that I can subscribe to in my app. Automatically subscribe to every one of their appearances.