Spotify, many months after we first saw its iPhone application, has submitted it to Apple. If Apple gives the mobile music app its blessing, then it could be on the App Store within days.

Although a demo of the iPhone application has been floating around for some time (a new version has been published, which is above), the real thing has been strangely absent. We know a few of its features - playlist creation and caching, offline playback, sharing, "similar artists" functionality and biographical info.

But there are a few things we don't know. How much it'll cost, exactly when it'll show up, and - most importantly - whether Apple's going to approve it. Spotify is confident - other music apps are there, but none are quite as touted as an iTunes replacement as Spotify is.

We'll keep you updated of the approvals process. Don't forget, you'll need to be a premium subscriber to use the iPhone app - which costs £9.99 a month.

Update: Spotify has confirmed that the app will be free to download (though you'll need to be a subscriber to use it), and commented on whether Apple will allow the app. Spotify's Communications manager, Jim Butcher, told Pocket-lint:

"We have a great relationship with Apple, think the iPhone is awesome and absolutely expect them to approve our app in the next few weeks. Apple has already approved several other music services such as Lastfm, Deezer and Pandora".

"We very much look forward to people being able to access their Spotify library wherever they might be and we've spent significant time and resources to ensure we've stuck to Apple's developer guidelines point by point".

Update 2: Spotify has answered a few popular questions that this announcement has brought up. An Android version is "still in development but coming along nicely". Offline mode works whether you've got a data connection or not - if you don't have an all-you-can-eat data plan, that could be useful.

It works fine on the iPod Touch, though you'll need Wi-Fi access to cache playlists, but there's no scrobbling to Last.fm yet on either the iPhone or the iPod Touch.