"The most recent paper to investigate the safety of ultrasound was just published [...] Of note is that this study used energy levels to tissue that were orders of magnitude higher than levels that uBeam’s system uses."

The abstract at http://www.sciencedirect.com/science/article/pii/S0041624X15...:

"Demonstrated in vitro, 0.6 W of transcutaneous ultrasound power transfer to an implant.[...] with an average RF input to electrical charging efficiency of 20%"

So, at best, 3W is "orders of magnitude higher than levels that uBeam’s system uses". That will charge your remote, but not your phone.