The challenge with E-Module Cloud is "calibration" and it may not be 100% accurate. The process is you estimate infinity (say 1/2 mile) and focus an object with your eyes through the E-Module cloud. The device records it, next you focus something at 10ft (you need to measure it) and then focus with your eyes through the device, and see what distance reading you are getting. If you are not getting accurate focus, then you need to re-calibrate your infinity focus, and repeat the process until you get desirable distance reading.
Hence there is a dependency on how good your eyesight is, which is also subject to change if you are in 40+ like me.
I didn't give-up yet, but didn't spend enough time to calibrate it. Will try again during Memorial Day Long Weekend, since your post reminded me about it.
Once you calibrate it, it will work nicely for portrait work. You will be able to mount it on the side of the camera and focus through your eyes, read the focus distance and align your Tech Cam's focusing distance and align accordingly.
Since DOF depends on where you are focusing, this device nicely shows the relative DOF based on your focus point.
Again, then catch is how well you calibrate it.
Subrata