DualShock 4 now wirelessly compatible with the PS3
It looks like Sony has updated the PS3's compatibility with the PS4's DualShcok 4 controller.
The DualShock 4 controller has been compatible with the PS3 using a USB connection since it launched with the PS4 but now it looks like it's wirelessly compatible as well.
To connect, plug the DS4 into the PS3 with a USB cable, select Manage Bluetooth Devices from the Accessory settings menu and scan for device, hold down both the PS and Share buttons and select the Wireless Controller from the menu.
The DS4's light should be white which means it's connected and you can unplug the controller. It's not fully compatible as yet as things like the PS button, vibration and Sixaxis don't work yet but at least you can get some functionality out of it if you want.