I bought my Sony A7r last summer for situations where low light and the need for speed were prohibitive on my Hasselblad H3D 39/Arca Swiss RL 3d combo.
At the time I tested the pretty basic Sony Smart Remote Control App. I wasn't very impressed TBH and since than I just used the fantastic EVF. However I recently updated the app and there is a huge leap in what it brings to the table.
You now get full control of white balance, shutter speed and aperture in all settings including manual mode.
It's really is very useful for architectural work, especially when tweaking lighting because the wifi works well (so far). You can walk around the shot taking test shots and adjusting things as you go. Much better than the Sony remote control where you have to stand on one leg reciting Ulysses in Japanese. I just tested the wifi, leaving the camera in one room and walked to the furthest point in my apartment and it works perfectly. Walls weren't an issue re. signal.
You can review the images in full size or 2meg. Full size is great for testing focus. 2meg is grand once you've focus 100% correct. Zooming in on the full size image previews on an iPad retina display is fandiddlytastic. 2 meg transfers quicker so it makes sense to use this file size after focus is sorted. A RAW file is transferred to your memory card once jpg and RAW are selected.
I have a few gripes though. You need to turn on and off the image magnifier on the camera and not on the app. The magnified live view image will appear on the LCD and iPad but it just means fiddling between devices. Maybe that's an update for the future.
Also it would be great to get a bracketing option which can be controlled from the iPad. Bracketing on the A7r is prehistoric in comparison to other cameras so agin hopefully that's an update for the future.
The EVF is fantastic on the A7r but if you're shooting something which requires you to move away from your camera location a lot it is a Godsend. The Camranger for Canon and Nikon setups is quite expensive. It's another physical thing you have to connect and charge and it's as buggy as Hell. This app does most of what it does and it's free!