For all of their popularity, Apple’s iPhones and iPads have sometimes been knocked for lacking the ability to accept USB thumb drives. With a thumb drive, users would be able to quickly and easily transfer files between their mobile devices and their computers. Microsoft has even been using the lack of a USB port on the iPad as a selling point in ads for its latest Surface tablet.

It’s not that you can’t transfer files back and forth between, say, an iPad and a laptop. It’s just that you have to use less direct, and sometimes slower, methods than you’re used to when using thumb drives between two computers. For instance, you can use email attachments, or cloud services like Dropbox, or you can transfer files via an obscure feature of iTunes. And, this coming fall, Apple is introducing a cloud-based file storage service and expanding its file-exchanging wireless AirDrop feature so it works between Macs and iOS devices that are near each other.

But, late next month, a small California company plans to introduce an actual iOS-compatible thumb drive called iStick. It’s specifically designed to move files in both directions between computers and iOS devices that use Apple’s current charging and syncing port, which is called the Lightning connector. It also allows you to view or play the files right from the drive itself, so you don’t have to transfer them and take up space on your target device if you’d rather not.

The company funded iStick on the crowd-funding site Kickstarter. It was seeking $100,000, but raised $1.1 million.

I’ve been testing an early, pre-production version of iStick and its companion app of the same name, and found that it does indeed work as advertised for file transfers. It still has a few bugs to work out before shipping, and the process isn’t quite as simple as it is between two computers, due to the unusual file system used by iOS. But the product works, and I suspect it will be welcomed by many iPhone and iPad users.

The iStick is a small, rectangular plastic device with a light-up slider button in the middle. You slide the button one way to expose a standard USB jack you can use in a Mac or PC, and slide it the other way to expose a Lightning connector you can plug into a late-model iPhone, iPad or iPod touch.

It’s made by a company called Sanho, based in Fremont, Calif., whose mostly Apple-oriented hardware accessories go by the brand Hyper. And it’s much pricier than a simple, commodity USB thumb drive. It starts at $80 for an eight gigabyte model, and ranges up to $250 for 128GB of storage. The company says the higher prices are required to license the Lightning connector and to meet stringent Apple requirements.

The iStick is billed as the first USB thumb drive for the Lightning connector, but there have been some predecessors. A company called PhotoFast makes a product called i-FlashDrive that works similarly, but it uses the older, wider, 30-pin connector and requires an adapter for the latest iPhones and iPads. And other companies have made thumb drives, such as AirStash, which have no iOS connector at all, and beam files to iPhones and iPads wirelessly.

In my tests, iStick file transfers worked between a variety of devices, including an iPhone 5s, an iPad mini, an iPad Air, a Mac and a Windows laptop. I was able to move and use files ranging from pictures, songs and videos to Microsoft Office files and PDFs — in both directions.

After loading up the iStick with files from your computer, you just slide the button to pop out the Lightning connector and plug it into the charging port on your iOS device. Immediately, the iStick app pops up; you use that app to view, play or transfer the files on the thumb drive to a local file repository on your mobile device. No wireless or Internet connection is required, and any files you’ve transferred to the on-device, local storage area remain available for use even after you remove the drive — again, with no wireless or Internet connection required.

The app is a simple, gray screen with four large, circular buttons. One displays files on the drive, a second one the files in local storage, a third offers quick access to the photo library on the iOS device and the last allows you to back up your contacts to the iStick or restore them from the iStick.

Three of the four buttons worked fine in my tests. The fourth, the Contacts backup feature, isn’t yet working, according to Sanho, but the company promises it will be working by the time the product ships.

By pressing the button representing the drive, I was able to play music and videos, display photos and view documents — right from the drive, and with little delay. Or, by tapping an icon, I could move one or more of the files on the drive into the local file storage area on the iPhone or iPad itself.

I could imagine popping the little iStick into my briefcase before a flight, loaded with movies, songs and work documents, and then using them right from the thumb drive during a flight, even without Wi-Fi, and without taking up space on my iPhone or iPad.

So, what about other bugs, and why is the process more cumbersome than laptop-to-laptop USB drive transfers?

Well, in the pre-production models I tested, the app had the wrong name. It’s called i-USBKey, and is intended to work with a companion device the company is marketing in Europe under the brand of its distributor there, called Bidul. The European product, however, won’t work with newer iOS devices using the Lightning connector, only older models that used the former 30-pin connector.

The apps are otherwise identical, and Sanho says the naming will be corrected by the time iStick ships. The i-USBKey app still worked fine with the iStick.

The cumbersome part comes in when you want to use a file transferred to the iStick local storage area with another app on your iOS device, and it’s due to the way iOS manages files, not an issue with the iStick itself. Unlike on a computer, iOS devices don’t have a visible, system-wide file system. Instead, files that can be used by an app can only be fully used, beyond just viewing them, via that app.

Apple gets around this using a function called “Open in…,” which offers a list of compatible apps when you press an icon in an open file. So, for instance, in my tests, I was only able to edit a Word document transferred from the iStick by pressing an iOS sharing icon at the upper right and then moving it to Word for iPad or another word processor, like Apple’s Pages.

Still, I found iStick to be a useful, if pricey, accessory for my iPad and iPhone, and one many users would value.