HDMI Switch Splitter 4K@60Hz, BolAAzuL Bi-Directional HDMI 2.0 Splitter Switcher 1 in 2 Out/2 in 1 Out HDMI Switch 2 Port Display Selector (2 x 1/1 x 2) 4K 3D HD 1080P
UHF Four 4 Channels Wireless In Ear Monitor System Stage Headphone Monitoring | eBay
This looks like a good idea. Alternative to expensive wireless IEM systems.