He was thinking of boosting the power of AM radio signals (.5 - 1.7 MHz) so the receivers could power the internal electronics. It would have hardly been "free" but it would be wireless. If we had gone down this route of wireless power it would make modern telecommunications impossible as it would bleed over every channel and dominate the airwaves. The real free power is higher up in the spectrum; visible light (400 - 800 THz) and photovoltaic panels for the win!