Like the Seagate GoFlex Satellite hard drive before it, Hitachi's G-Connect can act as expandable wireless storage for your mobile device. It can store 500 gigs and even has an ethernet port to turn itself into a router.
The ethernet port is especially convenient because it could do Time Capsule-esque duty: give you storage and internet access at the same time. The rest of the specs are expected, 802.11n, comes with an iOS app to connect to the HD, etc. One thing that's mildly sucky about the G-Connect though is that it needs to be plugged into a power source. Not exactly mobile. $200 [UberGizmo]