All these physics-debunking conversations seem to assume a single source. I naively assumed that UBeam will work sort of like the Gamma Knife (https://en.wikipedia.org/wiki/Radiosurgery#Gamma_Knife), where there are many sources that intersect just at your phone or device. This completely changes all the physics assumptions, and is a good reminder to keep an open mind.

That being said, I'd be highly skeptical of the health risks of this technology, especially given the only benefit is convenience.