Flying a UAV in airspace that may also be occupied by other aircraft using a connection where the call could be dropped could lead to loss of life. It's an interesting demo, but I think the FAA might have something to say about it.
This is very cool, but to answer your question about COTS platforms for military applications, I think it would need to be a modified COTS platform -- much like Obama's smartphone, which is off the shelf, but not a normal commerical product -- it was designed and manufactured by a defense contractor specifically for government customers requiring NSA-level encryption, secure OS, etc.
Do you think that using commercial communications platforms for military applications could ever take off, or are the security risks too great? And more important question, what is your favorite iPhone app?