Recently I've started using the Nike+ app on my iPhone to keep track of the distances and times when I go for a run in the park. I noticed that it has a power songs feature, which I haven't tried out as yet, I imagine it would allow me to specify particular songs that I can listen to while running.
When I try to use the power songs feature, it only lists the songs that I have in iTunes, I only have a small collection of itunes songs that I would care to listen to whilst running and would prefer to find a way of using the songs that I have on Spotify instead.
I have an unlimited Spotify account so I can store my playlists offline. I am not registered with Nike+.