It does 720p. But you are correct, for more money you can buy better.
But, that's not a video piece.
That's a USB to wireless unit. It doesn't allow for a standard piece of HDMI gear to send out to another location. Instead, you plug it right into your computer. In this particular forum, it may make sense that is what the user is after, but it really sounds like he wants to get his HD cable feed from a box inside the house to outside the house.
The product you listed is 100% incapable of doing that unless his cable box has a driver to allow for a USB PC connection which will actually work, which is extremely unlikely.
What he needs is a standard video connected product which can take full bandwidth video and send it out.
The Slingbox can't really do that, but it will do on the fly H.264 encoding, or similar, and send it to a receiving unit. A zone player. But, it is still going to compress the video signal and then decompress it upon arrival.
The wireless HD unit I linked to sends full bandwidth, uncompressed HDMI from ANY HDMI device he may have and then transmits it as an uncompressed stream to the receiver. So, the video put out of the HDMI source, is received pixel for pixel at the receiving location.
It maximizes video quality and allows for any HDMI source to be connected to it directly. Whether that's a Blu-ray player, game system, or cable TV feed.
The product you listed is pretty specifically, and uniquely, designed as a PC to display wireless adapter. These devices also typically don't run at full 60hz, but run at less than full frame speed with heavy encoding making motion video less than perfect. Not that this is bad if this is the goal, but I certainly wouldn't recommend it in a part of my home that I cared enough to convert to a TV watching area!