The must-have accessory for the PlayStation Vita launch -- and this is because you almost literally must have one -- have been Sony's proprietary memory cards. The 32GB versions in particular have been the most sought-after, selling out in Japan and being confirmed for the handheld's US launch.
If you're in Australia or Europe, though? Tough. You will not be getting 32GB cards when the Vita launches in February, a Sony representative on the PlayStation Blog saying "at this time we are not planning to launch with the 32GB PS Vita Memory Card".
PlayStation Vita AR Cards Bundled Free At Launch [PlayStation]