I've been listening to Radio Shonan for over two months now, yet I'm in Seattle! Here's why -
SimulRadio has it, and it can be broadcasted not only in Japan but all around the world... But this has stations that might be unfamiliar (this is
community radio, targeted to a particular demographic); however, I was able to listen to a number of Japanese pop hits, and even earlier this week I heard SCANDAL's new song "Taiyou Scandalous" on Radio Shonan earlier this week!
And, Zeke, there's also popular hits from the past, and maybe a mix of Western music as well.
http://www.simulradio.jp/
(See also:
http://www.jcbasimul.com/)