There are a lot of fly by night outfits out there. You must have found one. A direct connection could be blocked by apple in the future. It's best to go with a combination wife - usb device.
Some examples:
Airstash
"Easily access, transfer, and stream your files from AirStash® – the pocketable wireless flash drive for iPad, iPhone, and iPod touch! This app requires an AirStash device in order to work. View, import & export photos, wirelessly stream videos, music & podcasts, and view documents stored on your AirStash. AirStash+ is an enhanced alternative to the built-in web interface adding features only possible with a native app."
http://www.airstash.com/
SanDisk
" SanDisk Connect Wireless Stick is the flash drive reinvented to work with both your computer and your mobile devices."https://www.sandisk.com/home/mobile-device-storage/connect-wireless-stick
Seagate Wireless portable hard drive
"The new 500GB Seagate Wireless portable hard drive is the company's latest HD designed specifically for use with tablets and smartphones like Apple's iPad and iPhone."
http://www.macrumors.com/2015/01/04/seagate-ces-2015-new-products/
Allows you to access your own sd card and usb device
http://www.amazon.com/Dane-Elec-Media-Streamer-Mobile-Junkie/dp/B00IA8LLUW
suggested by seeblue
http://www.dpreview.com/forums/thread/3516024
Camouflage data files as a raw image.
read files from a flash drivehttps://www.youtube.com/watch?v=m5f1VmjjczQ
Kingston Digital MobileLite Wireless Flash Reader for Smartphones and Tablets (MLW221)
Kingston Digital MobileLite Wireless Flash Reader for Smartphones and Tablets (MLW221)
CloudFTP
https://www.kickstarter.com/projects/danielchin/cloudftp-wirelessly-share-any-us b-storage-with-ipa
https://www.amazon.com/HyperDrive-iUSBport-CloudFTP-Storage-Wireless/dp/B008U9GS 18
FlashAir™ II Wireless SD Card series
--Share photos & videos wirelessly
--Capacity 16GB
--Supports simultaneous access from up to seven devices
http://us.toshiba.com/accessories/wireless-sd/16gb/class-10/PFW016U-1CCW
Photofast's iFlash Drive
Here is a nice adapter. You can move data in both directions! Be sure to get the real thing.
http://www.photofast.com
review:
http://www.macworld.com/article/2036911/review-i-flashdrive-hd-a-flash-drive-for -ipads-iphones-and-laptops.html
Here is the ios app:
https://itunes.apple.com/us/app/i-flashdrive-hd/id525386291?mt=8