Myspace Instant Messenger is available on the Myspace mobile website (m.myspace.com) only on phones with advanced web browsers: iPhone, iPod touch, Android, Palm Pre, and Palm Pixi. Myspace mobile IM will log you in and handle conversations just as if you were on the full myspace.com website on your computer.
There's one major difference—you can only chat with friends, so you will appear as offline to any non-friends who browse your profile on the web.
You can choose to not sign into IM automatically on the IM Settings page.
Read more about Myspace Mobile (coming soon).