Al Azif has released a PS4 Homebrew that lets you test the rumble on the PS4 controller. While this might not sound impressive or groundbreaking, this release relies on the open source SDK from psxdev, and that makes it exciting for me.
Al-Azif had to make some modifications to the open source PS4SDK in order to get this to work, and hopefully those will make it to the main repository from psxdev.

You can download PS4Vibe from the developerís github.
You will need a hacked PS4 to run ps4vibe.
For now, the developer explains the homebrew needs to be loaded through OrbisLink (a compiled version can be found here but we havenít tested it. Better building it directly from source).