One way to do this is through this device which I recently bought and tested.
I like the idea of this device, but I’m worried about the cap which covers the micro-usb connection. You do have to turn it slightly counter-clockwise to loosen it and pull it off to the side. I’m not sure how long that mechanism is going to last.
This does work like a standard USB thumb drive for the computer. Getting it to work with your phone is a bit more tricky. Some people online seem to be able to plug and play, but not me.
Also – In the Play store do a Search for Sony File Manager and it should take you to the app they recommend. I installed the app, but it does not appear to work with a Nexus 4 or any Nexus devices. There’s a website on the back that will give you a list of compatible devices.
It’s a bit disappointing that this doesn’t work universally on all Android devices. It all depends on what particular phone you have. It also doesn’t work with any Lumia phones.
They do have some instructions online at:
If you have one of the compatible listed phones you might be golden, if not then you’ve still got a small thumb drive.