Vita's 3.00 firmware update, which preps the handheld for the PS4's arrival later this month, is live and available to download. The update's major addition is PS4 Link, an app that adds Remote Play and Second Screen connectivity between console and handheld.
Similar to the PS3-based feature, Remote Play will let you play "most" PS4 games on your Vita via Wi-Fi. As detailed by Social Media Manager Sid Shuman, it'll work best when the PS4 is connected via ethernet, and when the Vita is in "close proximity" to the Wi-Fi access point. As for testing that out for yourself, without the console the PS4 Link app is just a dirty little tease on the Vita home screen - hold tight until November 15.
The other aspect of PS4 Link is the Second Screen feature, which sounds similar but is significantly different. Second Screen lets you access additional content on the Vita screen, maybe a map or some weapon info. It's specifically for games that support it, much like Microsoft's SmartGlass tech for the Xbox 360. Second Screen will also be available on iOS and Android devices via the upcoming PlayStation app.