What is it with playlist apps on iPhone?

[aMUSEd]

There are several playlist apps that seem useful for creating playlists based on your behaviour such as Mood Agent and Groove as well as some that offer more editability than iTunes on the phone itself but why can none of them save a playlist in a standard format that can be opened in iTunes or another player? What I'm really looking for is to just be able to be listening to a song, think that sounds good I want to save it to a playlist for future, and do so without leaving the song. Anyone know an app that can do that? The Spotify app does just that but just for Spotify.