Say we have an iPhone that has mp3s synced to it that play normally with the built in ios music player. Can a webpage be coded in a way that if I surf to it using mobile safari, I can see my music library and play the files?
If so what APIs etc should I use?
On iOS, this is not possible. It is possible for Chrome Applications to get access to the local media library; however, iOS (even Chrome on Android right now, actually) do not support this.