I had a friend over one day, we got bored and found my old magic jack plus (http://www.magicjack.com/). We wanted to see if it could be reprogrammed, but upon plugging it in to the his computer my friend saw that it was registered as a sound card.
After finding two old phones, we hooked them up and played a song. Success! The speaker on the phone stand started muffling the sound, but the phone did that anyway, so the magic jack is not too blame.
Ten minutes later the phone handset was charged and I called my friend with Skype, the sound was just like a phone call. After a celebratory cheer the handset died. From this we can learn the magic jack has a lot strange features that no one would suspect.