The live feed service from BB2:
The BBC of course though on Freeview at least the only ones really in the market and although simple their original offerings had much more thought put into them than later efforts, being reskinned for each event.
Connected TV obviously now offers more potential but surprisingly of the main players only the BBC are really pushing it even though it could potentially offer easy access from within the channels to their on demand platforms and extra video streams when required for the commercial terrestrials. 4Music does offer access to three channels on Freeview, and strangely QVC offer a few extra channels via theirs but use a different interface on two different channels - QVC itself has a proper multiscreen but the other channel (36 IIRC) has a scrolling based menu.
I preferred the internet when it had a sense of humour.