I posted the same issue here http://community.wd.com/t5/WD-My-Cloud/Play-All-Video-File-Types-on-Iphone/td-p/672519 and no true answer.
One person suggested that you must download the video to the device before you can open it with a program. But i want to live stream it over my 4g instead of downloading it. Doesnt seem like it’s possible with this current WD app for Iphones. Works awesome on android.