Gizmodo has a post about the Radio YourWay from PoGo! Products and calls it TiVo for radio. It's closer to a VCR for radio than a TiVo. It's missing a lot of the things that make the TiVo special. The biggest of which are things like pause and rewind back a few minutes in while listening to 'live radio'. Still, it is a step in the right direction. Oh yeah, and it doesn't support seem to have Mac support.
What else would I put into this product if I was selling it. I'd bluetooth or WiFi enable it so that I could configure it from my computer easily without having to plug it in. I'd work on developing some kind of standard for radio stations to publish their schedules in so that I could browse what shows were on when and select ones to record (or does some kind of TV listing type thing exist for radio already?).