I looked at the product page you listed, and it looks very similar to two similar units I tried on eBay (and both failed, because they appear to simply be "rebadged" versions of the same piece of hardware)
Amazon.com: Mirabox HDMI Extender Over IP/TCP Cat5/5e/6/6e Rj45 UTP/STP Ethernet Lan Switch Network Support 400ft(120m) 1080P Full HD Extension, Black (HSV373 A Pair): Electronics
Amazon.com: AGPtek LKV373 100M HDMI Extender over LAN Routers/Switchers Ethernet Network RJ45 CAT5 CAT6-Single Source from 1080P Full HD STB,DVD,PS3 - w/DLP,LCD,LED ,Supports TCP/IP by Ethernet, DC 5V/1A: Home Audio & Theater
Neither unit worked in my environment, both receivers said the same thing (check source signal).
I do believe the problem is with my video hardware, though. My machine has a Nvidia GEFORCE video card with 3 ports - DVI, HDMI, VGA. The card will support 2 monitors, so I could have a VGA and HDMI, VGA and DVI, etc. My regular monitor is connected to the VGA port, and I tried connecting each of the units to the HDMI port. Even with these two units connected to the HDMI port and "on", the video card only detects a single monitor turned on.
So, I believe, its not sending a video signal out over the HDMI port, since it does not 'detect' a 'monitor' there.
After looking at your product page, I suspect the same thing will happen if I buy it.
I'm of the thought that, if this is to work with the video card I have, I would have to get some type of HDMI "splitter" to send the input signal to two output sources, while allowing for bi-directional communication from the HDMI monitor so the video card realizes there is something connected to the HDMI port, and activates the video on it.