MOG, the online demand music service whose accompanying mobile applications are among the best of the breed for streaming tunes to your handset, has just released its highly anticipated iPhone app upgrade. With the now iOS 4 compatible app, MOG addresses one its users' top complaints: no multi-tasking support.

Now the app runs in the background, allowing you to listen to music while working with other apps. This, plus a few other features, make the new MOG app the must-download update of the day.

What's New with MOG

The new iPhone 4-compatible MOG application can now be controlled with the iPhone/iPod Touch's built-in audio controls. When playing in the background, a double-tap of the home button reveals the multi-tasking apps. Swipe your finger left to right to reveal the audio controls for MOG. When the app is playing music but the screen is locked, double-tapping the home button will reveal lock screen controls.

The new app now also supports some external hardware devices, too, including third-party Hi-Fi docks, audio remote controls and headphone remote controls (1 click to pause/play, 2 clicks to move to the next track, 3 clicks to move to the previous track).

MOG vs Rdio

MOG, which offers about 8.75 million tracks at present, is going head-to-head with Rdio, the app backed by KaZaA and Joost creators, Niklas Zennstrom and Janus Friis. Although Rdio launched with 7 million tracks, it did so without having a firm deal with Merlin, a slight which seemed to incense Merlin's CEO, Charles Caldas. "It is incredibly disappointing that Rdio have launched their new service across North America without having finalized a deal for the world's most important independent labels and artists," he said. "We are surprised that a service, whose success would seem dependent on offering its consumers a comprehensive choice of repertoire, would launch without giving those consumers access to the leading global independent labels we represent, and their artists."

For those into indie music, many of Merlin's artists are household names. It represents Vampire Weekend, Arcade Fire, The XX, Neko Case, The National, Tom Waits, Spoon, Grizzly Bear, DJ Khaled, Dorrough and Tiësto, to name a few, through its members Rough Trade, Warp Records, Epitaph, Naïve, Tommy Boy, One Little Indian, Yep Roc/Red Eye, Beggars Group, Merge, !K7, PIAS, Domino and Koch/E1.

But services like Rdio and MOG are so new, it's unknown at this time whether a large catalog will actually be the top selling point for attracting new users. For now, MOG has the larger catalog, but Rdio offers unique features, like social networking integration and the ability to preload your iTunes collection into its service.

Rdio, MOG: Data Hogs?

One problem both services share is the ability to jack up your cell phone data bill. After a month of heavy streaming across an iPhone and an Android phone, our household's AT&T bill flew way past the 2 GB limit (on AT&T's "DataPro" plan), charging us an additional $10 per GB over. Although that's a reasonable, non-gouging price, when factoring in the $10/month for the streaming service, you're talking $20/month to ditch iTunes in favor of the cloud. Yes, it's all-you-can-eat music, but at these prices, that's a buffet many won't be able to afford.