On iOS I pretty much stick with Castamatic and Overcast, both are full native iOS apps but neither are open source. I'm sure there's something listed at http://www.NewPodcastApps.com which is iOS and full Xcode native.
UPDATE: 21 Open source apps written in Swift (including one I use every day: Firefox for iOS): https://medium.mybridge.co/21-amazing-open-source-ios-apps-w...