Well, some of these folks (and cyclades is another fairly popular one I meant to mention) provide drivers that provide direct port redirection (of COMs/TTYs) that can simplify things (if teh drivers aren't buggy!).

That was my original question... Do any of them offer source code so that you can compile the drivers for the empeg? None of the ones that I found give you source.

I was hoping to avoid having to do custom programming to interface with one. Since there's no standardized way that they use (each vendor does theirs differently), you'd either have to reverse engineer their protocol or write a hacked telnet client. Either way, it's not a drop-in solution.