There are several of these out there but I want to build one for myself. Cant find any schematics or explanations. Can anyone help explain how to approach this? BTW the HDMI is because of the hd quality and more importantly the low latency..

 

Unless you are an expert in high frequency analog and digital design, that's not a do-it-yourself project as most of the designs likely use proprietary and complex circuits, which are not available on-line. It's orders of magnitude more difficult to send HDMI as compared to sending an old analog NTSC signal wirelessly.