We can’t have a media extender conversation here at ZNF without mentioning existing TiVo boxes. Though, at this point, it’s really a tale of two cities: Series2 and Series3 units.
Networked Series2 units offer multi-room viewing (MRV), allowing the transfer and playback of recorded shows from one TiVo to another within the house. While we’ve been able to send MPEG-2 to Series2 units for some time now, the public beta of TiVo Desktop v2.4 software now bundles video transcoding functionality (.wmv, .mov, .mpg, .mp4) for $25.
TiVo Desktop software (for PC and Mac) also publishes photos and music from computer to both Series2 and Series3 (now in HD). If your particular audio file format isn’t supported by default, there are various methods (PC, Mac) to get past that. Now that TiVoCast has been enabled on the Series3, both they and the S2 should support Amazon Unbox video rentals and purchases in the near future.