I reverse engineered a store bought cable and made my own program only cable. Easy enough to do with a DB-9 and a cat5 RJ-45 plug. Sorry don't have the pinouts right now, but when I think to look I'll repost.
The software is a whole 'nother story. Pretty easy to program parameters, but the way it was written it's wonky as all hell. You will need a real serial port on your computer. I have yet been able to make it work with a USB/serial adapter. Then again, it will not work on all true serial ports. You have to shop around for a computer that works. It also likes to go into "crash mode" every once in a while. The only way to revive it is to power off the computer and reboot.
There are no help files worth mentioning, but hovering over a parameter will give a quick blurb of what it does.
Other than that, really straightforward to set an informer up.