RDS RadioText has been used for a decade or more now to display "now playing" information on the receiver screen. Most implementations of digital radio expand and build on such uses for metadata, however, and many stations are still trying to figure out how best to use the screen that comes with many DAB receivers.
James Cridland, formerly director of digital for Virgin Radio and now head of Future Media and Technology, Audio and Music, at the BBC, recently blogged an interesting personal example of the value of visual elements for radio:
I've been accustomed to seeing now-playing information on livetext (that bit of text you see on both DAB and Freeview screens) for a long while. Virgin Radio's tells you what's playing, as well as a snippet of information about the artist, for example; interspersed with programme information and the odd piece of commercial content.
But I've never seen fully contextual livetext in the middle of speech programming before. And I listen to a lot on BBC Radio Five Live and LBC (albeit less on Radio 4).
Cridland goes on to talk about the search possibilities and other value of visual elements for traditional radio.