Listening to a music with a friend comes with a few problems. Sharing headphones might be a little gross depending on ear cleanliness, plus you only get one earbud per person. MyStream is an app that lets you share that music wirelessly to your friend's iDevice so you can both listen to the same music at the same time.
MyStream's music-sharing abilities are also really nice if you're working with others who want to listen to your music. Maybe you want to share spoken word content with other people in the car, but without playing it on the car stereo. There are a lot of use cases for this app if you think of them, but each one is a little bit niche. Nonetheless, there are plenty of circumstances where MyStream can really come in handy. It's a good app for you and your iDevice-carrying friends to have in case you want to use it, seeing as it's free.
For MyStream to work, all you have to do is be on the same network as anyone else running the app and their devices will show up in the list of available streaming devices. One person needs to put a playlist together and the other person needs to connect to it. That's all that's involved in the sharing process.
The main disadvantage is that the listener's audio lags behind the source audio. It's only about a difference of one second, which shouldn't really be a deal breaker for anyone, but you'd think MyStream would be able to offset the source based on information from the listener's device. That's probably easier said than done, but it would be nice if the two devices could play the streams almost completely in sync with each other.
All of that said, we're talking about an app that works pretty well for providing its intended solution. At a price it might cause an adoption roadblock that would limit its usefulness, but for free MyStream is a pretty worthwhile download.
MyStream (Free) [iTunes App Store]