A picture claiming to be a mock-up of the PSP Phone has been shown on Techeblog.com.
It shows a widescreen 3-inch (480 x 272) display, PSP functionality via M2 card slot, dual-slide design, and a functional gamepad.
On one side there is a joypad with analogue stick for PSP controls; however, if you slide the phone to the other side you get the Sony Ericcson phone number pad.
More
here.