Your iPad already has a few gigs of storage space for you to take advantage of. Need more? The Patriot Aero 1TB Wireless Mobile Drive has you covered. It is a portable storage solution for tablets, smartphones, and laptops. It wirelessly stream movies and music with up to 5 devices. Free iOS, Android, and Kindle apps are available. The battery will last you 6 hours.
The Patriot Aero device has space for about 185k songs, 231k pictures, and 460 hours of video. It supports WPA2 connection. You can get one of these for $180.