I installed 4 basic cameras and monitors in my GS. For about $60 you can get a 12v camera and monitor. I am adding a DVR to three of them for drive time recording. I have monitors mounted on the visor.
Monitor - Supports 2 cams
https://www.amazon.com/dp/B019U500V4/ref=sspa_dk_detail_3?psc=1&pd_rd_i=B019U500V4&pd_rd_w=oH746&pf_rd_p=80559f3c-f83b-49c1-8a72-40f936e9df7a&pd_rd_wg=UQlEW&pf_rd_r=7F7YCDBMZG3N4072GA5N&pd_rd_r=a1a49089-3dcc-11e9-9741-2bc3fc200bcc
Camera
https://www.amazon.com/Camecho-Vehicle-Waterproof-Reversing-Cameras/dp/B00NGN7PWY/ref=sr_1_10?keywords=Backup+Reversing+Rear+View+Wa terproof+Camera&qid=1551628657&s=electronics&sr=1-10
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[email protected]/FI9816P_C4D6553DB5C4/IMG_0252.jpghttp://home.equinemediaworld.com/FI9816P_C4D6553DB5C4/IMG_0252.jpg
http://home.equinemediaworld.com/FI9816P_C4D6553DB5C4/IMG_0254.jpg