Backstory: I just listened to Art of Product episode #69 with guest host David Cohen. I was a little familiar with David but this was the first time I've heard him speak and I was blown away, I liked his attitude about startups and hard work. I tried to find his podcast or others he was featured on and it's not that simple.
The Idea: A podcast search platform where you can follow guest hosts.
Deep Dive: Similar to subscribing to a podcast, you would build an app where someone could subscribe to a person and any podcast they are a guest on, would pop into that feed.
Validation: This is a different take on consuming podcast content. You could MVP this by manually googling a few people and compiling a hard coded list on a landing page.
Monetization: You would have to monetize via ads.