I'll be the first to admit that I had a little trouble wrapping my brain around this one, but I think I've got it now. Sure the appeal of closed-captioned radio for the hearing impaired is clear, but what wasn't immediately apparent was why, precisely, one would want a standalone box for such information if you could potentially get it just as easily through, say, the station's website. This first iteration (which is very much still in the proof-of-concept phase) is intended for emergency relief organizations like FEMA and NPR and its partners are currently testing it out in the Gulf states. The box uses a tablet as a display, getting emergency information through the radio spectrum, so you can use it when the power is out and your WiFi isn't working -- assuming you've still got juice in your tablet, which powers the box.
At present, those emergency alerts are the only thing that are currently closed captioned, though NPR is aggressively looking at captioning most or all of its programming, so you could theoretically get the text narration through the box or through the public radio network's site. Future iterations of the receiver will also be a fair bit smaller, perhaps eventually being built into radios with displays, so hearing-impaired public radio fans can still get their Terry Gross fix.