I've long promoted the BBC's iPlayer as a fantastic example of how digital distribution should work, notwithstanding the few flaws Riyad espoused recently. With the rollout of downloads for portable media players, the BBC just added yet another feather to the iPlayer's cap.
Similar to PC downloads, the media player files are protected with DRM, so only certain players can play them. The BBC has tested using the Sony Walkman E and S series, Archos 605 WIFI and Internet Media Tablet, Philips GoGear 52xx series, Samsung YP-P2 and YP-Q1 and the Nokia N96. However, there should be no reason why any media player compatible with Window's DRM can't play downloaded files.
For the interested, these files are encoded in 320 x 180, WMV with 500kb/s video and 128kb/s audio. Newly released programs are already being encoded in this format. While not explicitly stated in the announcement, it seems reasonable to assume that PMP files will also have restricted playback time.
P.S. Incidentally, I highly recommend everyone checks out Dirk Gently's Holistic Detective Agency: The Long Dark Teatime of the Soul on the radio side of the iPlayer. That concludes today's broadcast.