The camera in the iPhone is fast and easy, but it's still limited to what it can do. If you want to step up the quality of images you're sharing on Facebook, Instagram, or any other social network with your fancy DSLR, then you would need to download the images to a laptop computer and hopefully have Internet Access. A simple approach could be to send it wirelessly from your DSLR right to your iPhone (which should already have Internet access).
YouTube member 1sicknickel shows how the Eye-Fi Wireless SDHC card works with the Canon 5D Mark III [Thanks Peter]. From your iOS device you'll connect directly to the Eye-Fi like a hotspot and see images taken with your camera. This is not exclusive to the Canon DSLRs, as it will work with many cameras (including many point and shoots). Check out the Eye-Fi SDHC cards via Amazon (Click Here).
What is Eye-Fi? It's an SDHC card with built in wireless capabilities to send the photos or videos directly to a computer or uploaded to the Internet (originally). Well with Eye-Fi's new Direct Mode on the Mobile X2 SDHC card, your camera will automatically send the image from your camera directly to your Tablet or SmartPhone via an Ad Hoc network (directly). This includes iPads, iPhones, and Android devices. You'll need to configure the card's wireless settings (just one time), and then from there it's all gravy. The new Mobile X2 is available now, and older X2 cards might get this feature via a firmware update. This totally simplifies the workflow for Photographers that often use this wireless tethering technique to view images with their iPads for a full blown view on Exposure and Color Balance. Heck, might be a good way to dial in your video exposure settings too.
Yeah I know what you're thinking. Only cameras with SDHC so what about Compact Flash shooters? From what I remember, the cards even work with Compact Flash to SDHC adapters. Keep in mind that by using this technique you'll be dropping the speed rating down enough that the camera might not be able to shoot HD video. Of course still photos should hold up pretty well. Check out some of the adapters below.