TrustedReviews have looked at the Samsung SyncMaster 940UX USB Monitor.
A quote from the article:
Samsung SyncMaster 940UX USB Monitor Review
The DisplayLink technology that Samsung has embedded into the SyncMaster 940UX is truly superb, simple as that. Being able to hook up multiple screens digitally, over USB is an inspired idea, and a welcome feature for anyone who uses a notebook as their main computer.
Samsung SyncMaster 940UX USB Monitor Review