Music subscription service MOG finally unveiled its long-promised mobile app today, with support for both the iPhone and Android devices.

The app itself is free, but using it requires signing up for MOG’s $10 a month premium subscription service that includes access from both the mobile phone and users' home computers.

Making a smartphone app available is a must-have for any cloud-based music service, as it allows users to take their music with them on the go. Streaming music to smartphones replaces the clunky file-transfer model of pre-smartphone devices that services like Rhapsody had to rely on in the early days of the subscription model.

But MOG hopes to set itself apart from the others by adding a more robust download-and-store option to its mobile app. Streaming music from the cloud is fine, but it requires a connection to either a WiFi or cellular network. And with AT&T recently putting bandwidth caps on its data packages, streaming may not be as easy a concept as originally thought.

So MOG and competing mobile music apps allow users to cache songs on their phone to play when not in coverage. Most limit that ability to simply saving playlists created on the Web. But MOG takes it to a new level by allowing users to select and save individual songs.

From the release:

MOG Mobile features include:

· Unlimited downloads: Download any song or album directly to your phone and can continue to listen to music even when out of cell or WiFi range.

· On-demand streaming: Unlimited listening to any artist, album, or song at any time.

· MOG Radio: Only MOG offers the patent-pending “MOG Mobius” music engine, which enables users to control the mix of similar artists, from true "artist only" radio up to a full mix of similar artists.

· Playlist access between website and mobile: Make playlists on and access them on your phone. Favorite tracks that are bookmarked using the mobile app are then integrated into a user’s personal library.

· High quality audio: Songs can be downloaded at the standard rate of 64 kbps or users can turn on HQ downloads (up to 320 kbps) to save the song as a larger file with higher audio quality. This gives users the option of receiving high quality downloads for maximum audio fidelity.

Billboard spoke with MOG CEO David Hyman on the eve of the launch, where he shared a few extra tidbits:

On marketing the service:
“We haven’t leveraged our [blog] network at all yet because we’ve been waiting for mobile to launch. We haven’t spent a penny marketing MOG to date. We haven’t run any ads on our blog network. Our affiliate network for the 1,200 blogs on our network haven’t launched yet. You haven’t seen an ad yet. But all that starts now. We have a pretty robust budget to do tests to find the avenues that provide the most efficiencies. The goal is to bring in subscribers that are lower [cost] than your lifetime value of the subscriber.”

On the lack of multitasking:
“It’s two weeks away. I just didn’t want to hold it. In two weeks there will be an update to the app. We’re all just chomping at the bit.”

On AT&T’s data limitation:
“Our app is the only one that lets you download songs instantly from the phone. We make it ridiculously easy. You can just pick any song and download it to your phone. Our 320 kbps is double that of your typical iTunes download. It’s very high quality. So if you’re concerned about data usage, you can just fill up your phone with music.”