Apple's AirDrop file-transfer feature sounds an awful lot like it relies on Wi-Fi Direct: Wi-Fi Direct hasn't yet found its way into any desktop or mobile operating system as a built-in component. Wi-Fi Direct allows ad hoc-style connections between devices (computers, peripherals, mobiles, and others) using robust WPA2 security. Devices advertise services as part of the SSID broadcast, such as noting that they can be printed to.
AirDrop is a no-fuss way to swap files between two Macs running the Mac OS X Lion release, still in a preview/beta test phase. It notes specifically that it works wirelessly. I suspect Wi-Fi Direct underlies this. Apple already has Bonjour networking built in to all its computers, and relies on this feature being in most major printers. Bonjour announces services when you're connected to a network in a manner conceptually similar to Wi-Fi Direct.
AirDrop doesn’t require setup or special settings. Just click the AirDrop icon in the Finder sidebar, and your Mac automatically discovers other people nearby who are using AirDrop. You’ll even see contact photos for those who are already in your Address Book.
We'll find out eventually. Having Wi-Fi Direct built into an OS would mean opening up that OS to setup-free connections for printing, file transfer, tethering, and other purposes in a way that's much simpler than today's network connection and service configuration pains.
Update: I had a briefing with Apple. It is not Wi-Fi Direct, but it is awfully similar.