I’ve been there before: I’m working, I’m listening to some Oasis or Death Cab for Cutie on iTunes on my Mac, and iCal reminds me I have to go out. I take my iPhone, I quit iTunes, and I realize I was really liking the song I was listening to. So I’m forced to fire up the iPod app on my iPhone, find the song again, and start listening from the beginning of the track. I could manually move the on-screen cursor to the exact position the song was on iTunes, but it’s quicker this way, plus I really have to go out. Seamless, a new iPhone app by Five Details, provides the simplest solution to this problem: a button.

Once installed on the Mac (for free) and on your iPhone ($0.99 in the App Store) Seamless will communicate with your Mac to see what song is playing. If the song is found on your device’s iPod library and you’re ready to leave your computer, tap “Transition Music” and the song will quickly fade on your Mac, and magically start playing on the iPhone. Same position, same song, one button. You can do the opposite, too: you’ve just got home, with a song playing on your iPhone. Tap the button, and music will start playing on your Mac . This happens in less than a second, provided that both devices are on the same local WiFi network.

While Seamless is intriguing, clever and almost magical in its concept, there are some execution issues to iron out. For instance, I couldn’t get the app to work last night (it kept saying the “song was not present” on my iPhone, but it was) and the developer told me it’s because of a bug that won’t find songs on a synced device unless you’re playing from a playlist – not just the Music library. So I created a playlist, synced it to my iPhone, and now the app works just fine. This bug will be fixed soon with an update, I was told. And of course, the app won’t work at all if you don’t sync music – don’t expect Seamless to be able to transition music you haven’t synced on your iPhone.

As long as you keep in mind that this version might require syncing a playlist and that you can’t just transition music you don’t have on your iPhone, Seamless is a great idea. It’s simple, and it’s only $0.99 in the App Store. Check out the promo video featuring the omnipresent Adam Lisagor below.