Q: Can iPad use an SD card as an external drive to read data such as movies, photos, music?

Technically, if you follow the naming convention, you can use an SD card to get photos and video onto your iPad. Now the catch is that you can't stream from, you have to import, watch, delete.

And you cannot use it to transfer music. You also cannot write to the card, only read off the card.

There are various wireless  harddrives out there. One of the first was the Seagate GoFlex that made its own wifi hotspot that the ipad could stream from. Poke around Amazon and you may find something that works for you. (I don't use one so I don't have anything to recommend)

There are some wireless external hard drives that can be used with the iPad.

Best iPad External Hard Drive Storage Options

http://www.unlocktips.com/2012/11/best-ipad-mini-external-hard-drive-memory-stor age-options/

iPad Storage Solutions

http://www.ipadstoragesolutions.com/iPadWirelessStorage.php

SanDisk Connect Wireless Media Drive

http://www.sandisk.com/products/wireless/media-drive/

WD My Cloud

http://www.wdc.com/en/products/products.aspx?id=1140

Another option:

Expand your iPad's storage capacity with HyperDrive

http://www.macworld.com/article/1153935/hyperdrive.html

On the road with a camera, an iPad, and a Hyperdrive

http://www.macworld.com/article/1160231/ipadhyperdrive.html

 Cheers, Tom

You can use a Micro SD card (supplied) in conjunction with a wireless flash drive to share photos, video, music and documents.

http://www.sandisk.com/products/wireless/flash-drive/