In the days when MTV mainly played music videos, on-air dedications were a big element. Now there’s a new iPhone app for that called MTV Dedicate, which takes the idea to social networks.

Released in the US only for now as a free download, the app invites people to “dedicate your favorite music videos to your friends on Facebook or Twitter or via email”, choosing a video then writing text to accompany the dedication.

“The music video and your custom dedication will appear on their Facebook news feed, Twitter feed or in their email inbox,” explains its App Store listing. “The person receiving the dedication will be able to watch the video from their home computer (mobile playback not supported at this time).”

That last caveat is disappointing, given the huge mobile usage of Facebook and Twitter (and email, for that matter). It’s unclear why mobile playback has been left out at launch, but it will surely be added at a later point.

MTV Dedicate is one of 60 iPhone apps released by MTV in the US, joining games, second-screen TV apps and music apps like MTV Music Meter, MTV Iggy and CMT Ultimate Fan on the App Store.

The app is free and seemingly ad-supported, judging by the screenshot showing a Starbucks banner ad on MTV Dedicate’s App Store page.