There is no need to get a special USB monitor now because Sewell has just launched their display Adapter that could convert VGA/DVI/DVI-D/HDMI to USB. Their latest product is the USB-to-HDMI version called HD Deck SW-31000, where you can actually turn any HDMI compatible monitor to your external/secondary display even your laptop/desktop doesn’t have any HDMI port.
All you need it to have USB 2.0 ports and you are all set. USB 2.0 interface supports about 480Mbps of transfer rate, which is pretty rich and more than enough to provide a high-end video connectivity.
For other supports, Sewell HD Deck SW-31000 also supporting HD video and DirectX games like StarCraft 2. Sewell HD Deck SW-31000 USB-to-HDMI display adapter has come with a CD installation containing the DisplayLink driver, which is the stuff that you need to make the adapter works flawlessly on Windows OS (Windows 7 supported).
Sewell HD Deck SW-31000 USB-to-HDMI display adapter is going to retail for $99.95. Also check out their USB-to-VGA, USB-to-DVI display adapter for your older LCD monitor (without HDMI support).