ESX itself does not have the capability to virtualize USB connections. VMware Workstation can do this though.
We have some of the Anywhere USB devices and while they do work great and are seemingly supported by VMware (See this article) they have definite limitations that may not work for everyone.
a) Each Anywhere USB device requires a static IP. If your short on IPs this may not be a good solution.
b) Each Anywhere USB device can only be attached to a single VM, you can attach 5 USB devices to that single VM though.
c) They cost about $250 each.
d) Mine only came with a 120V AC adapter.
The documentation that comes with them makes it pretty clear that they were originally designed for Point Of Sale (POS) applications with thin clients. Working with ESX is just a side benefit.
So if your need is just to attach a single USB dongle to your ESX VM then the Anywhere USB device would be my first choice.
I use one of them in my DMZ environment where I only need to have a single dongle attached.
If you need to attach a dozen of them like I have to do for R&D purposes then you need this software. You need a dedicated or semi-dedicated workstation or server with the USB over Network software installed on it and the USB devices attached to it.
We use this software in our main R&D network and have several dongles, scanners and printers attached.