According to engadgetmobile.com. The SDK allows developers to create custom, interactive panels for the touchscreen QWERTY’s Panel Interface. Sony Ericsson claims that, “The Xperia X1 will offer the richest mobile user experience, putting the world at the fingertips of the user.” Sony Ericsson will offer a panel download service in the future, showcasing all the panels built by all developers.
The Panel Applications are meant to be simple, rich, and fully-interactive allowing quick access to your data — eMail, calendar, multimedia, games, IM, etc. Check the video @ engadget for more info
Now the wait begins for developers to get theirs hands dirty , so what Panel are you looking to get ?
More info : sonyericsson.com