From the Vemedio blog:
I am happy to announce that Instacast for Mac is available for download as a free beta version. We’ve been working very hard for the last 4 months to bring everything that you love from Instacast on iOS to the Mac. While it resembles a lot of similarities to the iPhone and iPad app, Instacast for Mac is not merely a port of the iOS app, it is a true OS X app in every possible way.
Good news, but I’m unsure if I really need Instacast on my Mac. Listening to a podcast with my iPhone docked into my iHome works just fine; I don’t see why I need a dedicated Mac app for it.