Shamless plug coming up....

http://www.componentbin.com/index.php?location=shop&category=37&action=viewcategory

Our smart module can do this, infact I've got code for it (would take 5 mins to get up and running on that particular module). I ran out of serial ports for some ATE stuff I was doing for a product we make for a scientific company, so I resorted to doing serial<->ethernet. Worked very well.

Ignore the out of stock..it's not actually true in reality.