It's a cool idea but it didn't get very good reviews on amazon. Or at least it got one really bad review, one useless review and no good ones.
This is the first product that can extend the use of portable electronic devices from a standard passenger seat. This revolutionary new cable has a patented design that coverts the audio output from the passenger seat to regulated power for small personal electronic devices. Our new version adds an optional battery BOOST to increase the power supplied and offer continuous power. Simple to use, airplane, bus and train safe.