The Samsung GT-I9000 Galaxy S adds Wifi Direct Certification to its spec list and is one of the first devices, and the first smartphone to be on the certified list. Wifi Direct is a new technology which attempts to remove the need for a router, and two devices can be connected wirelessly to enjoy the transfer speeds of b/g/n. Only one of the two devices have to be Wifi Direct enabled for the process to work. The other smartphone on the certified list is the LG KU5900.
For those users who already have the GT-I9000, adding Wifi Direct is easy with a software update. The hardware can stay the same. It is not clear when the device will get this update but it's pretty safe to assume that this feature will soon be added to other smartphones too.