The GoFlex Satellite is a 500GB drive that acts as its own Wi-Fi hotspot. First you have to connect it via USB to a PC of some sort so you can transfer the content you want onto the device. The "magic" of the drive, though--and why it works while my Iomega probably can't--is that Seagate has developed an app to act as a front-end for accessing the data in terms that iOS can understand.
The GoFlex Media app is available for free from the Apple App Store. You can't access the data while the drive is connected to the PC, so you have to disconnect it first. Then, the Seagate drive will show up on your list of possible Wi-Fi connections. You connect to the Seagate Wi-Fi, then access the data through the Seagate app.
The plus side is that the device works on a rechargeable battery and it can stream data to multiple iOS devices simultaneously. It could come in handy for storing a music and video library to be shared among the family on long road trips.
However, I wasn't completely impressed. I copied my entire music collection to the device--enough music to play roughly 23 days without repeating a song. The GoFlex Media app just lists the thousands of songs alphabetically. It doesn't sort by album or artist. It doesn't even list the artist or album name in the details--you just have to guess based on the titles of the songs.
I also did not appreciate listening to the high-pitched whining from the drive as it accessed data. The constant beeping and chirping was subdued, but loud enough for me to hear it, and loud enough to annoy me. A more concerning issue is that there's no security in place by default. You have to go into the settings on the app to change the name of the Wi-Fi network so it isn't obvious that it's a GoFlex Satellite, and assign a password so that every device sitting in range of the drive doesn't connect to it and access your data.
I assume the Kingston Wi-Drive is similar, but I haven't used that one. Overall, the GoFlex Satellite is a promising concept, but Seagate has a few issues to refine for the next version.
The iPad seems uniquely suited for online data storage. The tablets have relatively small internal storage capacity, and the lack of USB ports or SD memory card slots (without the aforementioned hackery) leave you with little option other than turning to the Web.
Thankfully, there are a variety of great options available for online storage. Many apps like DocsToGo, are capable of connecting directly with Google Docs, Box.net, Dropbox, iDisk, and SugarSync. The Apple iWorks Pages app can connect with iDisk, and also with other services that offer a WebDAV API of some sort.
I use Box.net already, so this connectivity gives me a variety of options. First, it provides a familiar file and folder sort of structure for my documents. Second, it lets me share one copy of the files among a variety of Web-enabled devices including my iPad, iPhone, and PC (when I was using it as well), so I don't have to worry about different versions or syncing.
When Apple's iCloud becomes available this fall, it will provide another online storage option. Like Box.net, Dropbox, and the other services already mentioned, iCloud will sync documents from one device and make sure that other iOS devices or PCs have that same data.
iCloud will have two distinct advantages. First, it will be seamlessly integrated into most of the default apps in iOS 5, and tools that are native and seamlessly integrated almost always work better than third-party add-ons. Second, it doesn't just store and sync data, it will also automatically and seamlessly back up and sync music, photos, apps, books, email, contacts, and calendar events--making it a much more comprehensive solution than the others.
There is also one significant caveat to iCloud--it is iOS-centric. Apple includes Windows PCs in the mix, but if you have a Linux PC, or if you use Android, or BlackBerry, or WebOS, for your smartphone or tablet, those will not be able to sync with iCloud.
I am looking forward to iCloud for all of the other benefits it brings to the table, but odds are fair that I will continue to rely on Box.net for storing and syncing my documents, spreadsheets, and other data so I still have the flexibility to use non-Apple devices if I choose.