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Every one of these podcasts should be available on iTunes, easy to use with iPods or iPhones. Otherwise Freakonomics has written about other options and hopefully you can think of some way to get started.
Personally I paid $6.50 for BeyondPod Pro for android, because it has some neat automatic podcast listening queue management.
Fun fact: podcasts are get their name from "iPod Broadcasts"
Can the creator change the way it unlocks by supplying a key in the form of an app.