The gMusic iPhone app from Interactive Innovative Solutions does what Google failed to do when it launched its Google Music Beta -- natively stream your Google Music tracks to your iPhone, iPod touch and iPad (as an expanded iPhone app). The Google Music service serves as a digital online locker that can store up 20,000 tracks from your music library.
The app is a basic music player that lets you browse your tracks via album, artists, genre and song. It also accesses your playlist information and lets you add songs to existing playlists. You can also create an instant playlist on the fly. It's great for on the go listening as your music will stream over Wi-Fi or 3G. It'll also play in the background so you can use other apps while listening to your music.
This gMusic iPhone app is available from the App Store for US$1.99.