Macworld has just published an article of mine that was fun to write: “Take Better DSLR Shots Using… Your Smartphone?” I look at three devices that control a DSLR wirelessly using an iOS device: the CamRanger, CameraMator, and iUSBportCamera. Although similar in general, each device has its own advantages and disadvantages, which I detail in the article. From the introduction:
Photos are meant to be viewed large. Yet when taking a shot—that crucial moment when we should be most discerning—we usually rely on the camera’s small LCD to preview the image. The traditional solution has been to “tether” the camera to a computer, so you can view shots on a large screen as they’re captured, or even control the camera’s settings and trigger the shutter remotely. That approach lets you correct the scene or settings and reshoot immediately if anything looks amiss.
But tethering can be limiting. Setting up a laptop on location is often inconvenient—and even if you’re shooting in a studio, tethering typically involves snaking a USB cable between the camera and the computer.
I think the headline is a little misleading, since I specifically talked about using an iPad and the iUSBportCamera app is just for the iPad. But I can understand that “smartphone” is likely to draw a bigger audience.
Jeff Carlson | Never Enough Coffee Creations 
Still want the smartphone article!!
The CamRanger and CameraMator work with iPhone and iPod touch, so everything about them applies to what you can do with a smartphone too.
Are you familiar with Canon’s WiFi smartphone app? Works with the most recent WiFi enabled DSLR Canons (6D, 70D)
http://www.usa.canon.com/cusa/consumer/standard_display/EOS_app