Wanted to mention our new App "DuoVid", which was launched in June 2013. Our App is the first App of its kind to play 2 videos at once side by side on the one iOS device. iPhone, iPad, iPod Touch. It's only 99c to purchase, but allows you to compare (use if for before & after videos - great for sports), improving & mastering your technique, and learning new skills.
You can use videos from your local device as well as search via YouTube. In a new update (coming soon), you'll be able to import via a URL feed.
DuoVid is great for song writing or even comparing your musical abilities to the pros on YouTube (like learn new riffs).
See more details here, as well as links to the App store. DuoVid by PitchanApp.com
We welcome your feedback also.