I can't see this being useful for most HTPCs.
It's USB 2.0. The usb end looks small, which means it's probably just an antenna - not big enough for video hardware.
Now, USB 2.0 has a maximum throughput of 60MB/s. Uncompressed 1080p at 24fps is something like 95MB/s. 60fps is around 120MB/s.
That means the device has to compress the video to send it (anyone image-quality conscious will turn away at this point). Since there doesn't appear to be hardware on the usb adapter, it means your processor needs to compress it. Compressing 1080p is a lot of work - especially when the computer has to decompress it from the original source at the same time.
Most HTPCs aren't really designed to be CPU power-houses. You can see how this would create an issue...