The next killer app for the iPhone? My bet is the Spotify music streaming service. It’s already available for the iPhone in Europe and will likely be part of Spotify’s rollout in the US later this year. I’m already a big fan of the service which basically gives you fast and great-sounding access to tons of music “in the cloud”. You can’t buy or download the music but as long as you have a net connection, a huge jukebox is available for you to choose from. In Europe you can use it for free (and put up with ads) or pay about $15 a month for the premium ad-free service [you can access the free version from here by using a VPN service like My Private Network]. If it saves you two impulse buys of dodgy albums a month on iTunes, then it pays for itself pretty quickly. As more leading artists put up material on Spotify, it could very well threaten iTunes as the leading digital music delivery system. Having a global jukebox available on the fly on the iPhone will be pretty damn cool.