Sony Ericsson seems to be working on another Xperia X10 variant. Code name Shakira, this device has a screen-size in between X10 and X10 mini, somewhere around 3″.
When the device was spotted it was still running Android 1.6. No other details are available currently.
Adding on another front, we last reported about the existence of a walkman series Android phone, it seems to be a really entry-level model, without 3G or WiFi and it is called Sony Ericsson W150.