Luminex already have a 2 universe Artnet interface on the market and an 8 universe interface: Node2 & Node8 - they've been around for some time... Both are available with wi-fi option too.
http://www.luminex.be/products_overview.php?cat=1
Give us a call if you need to get hold of one
The new interface is a 4 universe device. (not available yet) They are also offering the ability to change the DMX connectors from just female (existing) to male as well at time of order - if you want a box with 2 ins and 2 outs (for example) - rather than using adaptors or m-m cables.
There are a number of cheaper alternatives on the market - 2/4/8 port - that don't have as many configuration tools - they all do the basic job of DMX-Artnet/Artnet-DMX conversion... I like and own Luminex Node8's as they are very flexible and configurable.
Peperoni USB are cheap - but I've had experience of them dropping out - I have a Rodin T & Rodin 2 - either work for DMX input (but not both at the same time... the latest plugged in takes priority) There is currently no facility in catalyst to route DMX to a Rodin 1 or T for DMX output. - I seem to remember that you can't do simultaneous DMX in and out on a Rodin T anyway - irrespective of catalyst.
Use artnet - its more reliable....
S