This $150 music player connects to devices via bluetooth, so you could link up your iPhone and access your playlists while out in the park. It uses an e-ink display to show power levels and other information, and a strap in the back where you can hold your device as well as charge it from the Rukus internal battery if needed.
The only information I can get about the solar panel is weak at best. It is a "high efficiency monocrystal solar panel" but no one seems to know the watts. I'm guessing probably 2ish Watts based on the size. I'm told that it can provide enough of a trickle charge to keep the music going all day, but I think most people will still likely rely on charging the internal battery through a wall outlet and use the solar panel as a convenient after-thought to hopefully keep the battery from going dead. In this video from Slashgear, the only extra info is that as long as there is sunlight, it will keep playing.
From the look of the products at the Eton booth, it seems that the company has simply taken a liking to putting solar panels on things because, perhaps, it's "cool" or maybe to offer yet another option for items like a roadside/emergency device. However, even on the new FRX series of safety products, the FRX3 has a tiny strip of a solar panel which, the representative at the booth said would take a really, really long time to charge the battery. She was right about that but not about the solar panel itself -- when I asked her the capacity, guessing at 0.5 Watt, she said she thought it might be a 10 Watt panel. Um, No.
Anyway, this boombox has a much larger, much more practical panel than some of the other devices, though I'd like to be able to get better information on whether or not it is really worth adding this on to the Rukus. There is a non-solar version, and you can bet this solar version has a larger footprint for embodied energy that will take a whole lot of parties in the sunshine to break even. Go for this model if you're always outdoors playing music, and go for the cheaper non-solar version if you just simply want a portable speaker set.
The solar Rukus is going for $150 and the non-solar version is about $50 less.