A photo of a Cyber-shot branded Sony Ericsson mobile phone appeared on a German discussion board.

Update 02/28/06:
Sony Ericsson Cyber-shot K800 and K790 Officially Announced!

The photo shows supposedly the mysterious Sony K800 or also called 'Wilma'. Engadget followed Wilma since a couple of weeks. All their photos look different from this one (via Widgx).

The Sony Ericsson K800 features a 3.2MP digital camera and the sliding cover lens design from the Sony Cyber-shot DSC-T series.
It makes totally sense for Sony Ericsson after the success with the Walkman phones to use the Cyber-shot brand on Sony Ericsson camera phones.

There is also a scan of a specification sheet posted in this thread on Telefontreff.de. The scan reveals quite a lot of details about the K800. First off, it is supposed to be a 3G mobile phone.
Measurements of the K800 are 106x47x18mm and the weight is 115g. The K800 features a 2 inch color screen with QVGA resolution, Memory Stick M2 slot, 64MB internal storage, Xenon Flash, 16x digital zoom, red-eye reduction, image stabilizer, FM-Tuner and USB 2.0.
The photo and the spec-sheet look pretty real to me. Albeit the jury is still out if the leaked information about the K800/Wilma are for real, I tend to think they are actually real.