Apart from your Nexus 7 and your SD card full of great photos, you’ll need three things:
From here, the process is delightfully simple. Download and install the NMI app. Next, insert the OTG USB cable into the micro USB port at the bottom of your Nexus. That then leaves you with a full-size USB port, into which you’ll pop your SD card reader and of course, your SD card.
You can then open the NMI app (it will ask you if you want it to automatically open when you connect an SD card) and browse your files, saving the ones you want to your device.
From there, you can open any of your photos as normal with apps like Snapseed or Instagram to edit and share to your heart’s content. If you’re a budding photographer, being able to quickly review your images on a bigger screen — to check for correct focus etc — could be invaluable, especially as the Nexus is much easier to haul around than a laptop.
It’ll work with the Nexus 7 and the bigger Nexus 10 and the cable works with the Samsung Galaxy S3 without needing the app — a browser automatically opens to show your snaps. I don’t have every Android phone made to hand so I’m not sure what the results will be on other devices, but for the cheap price of the cable, it’s probably worth a punt anyway.