Ripping off the Wiimote, with the Sixaxis, wasn't enough for them?
When the PlayStation 3 first came out, people complained about two things. The first was that the "Sixaxis" controller was lacking Dualshock, therefore no rumble, and the second was that the Sixaxis controller ripped off the Nintendo Wii's "wiimote" in the way that it was motion sensitive.
However they released a Dualshock 3 recently, so at least that problem was fixed. Now Sony is working on another controller for the PS3, with the ability to "break apart" into two separate units. Each part will contain an accelerometer for motion-sensitive functions. The Wiimote, along with the Nunchuk, also makes up two controllers. They don't combine together though, so Sony are showing some originality there.
Sony are hoping to rope in audiences like the Nintendo Wii did, with games that are more family friendly. With the release of High Definition Blu-Ray games, the release of Home later this year and the steady improvement of the Playstation Network, Sony Computer Entertainment are hoping to hold the "best all-round home entertainment unit on the market."
The Sixaxis that was originally released with the PS3 had very limited motion-sensitivity and Sony is hoping to improve upon it.
No images have been released of this creation as of yet, let's just hope that we won't get a black Wiimote with the Playstation symbols on it.