I have done this at a couple of jobs and it does work. Here's what i know:

You have to use the 232 cable that comes with niles and this has to be directly connected to the rti 232 cable. This took me a day to figure out.

Next you should follow niles' instructions about clearing the firmware of the gateway and then redoing the firmware. There are instructions on their website.

The programming is kind of funky for my taste. However, first you have to tell the gateway which zone it is controlling. Then you tell it what source and commands. I've found that you should get one niles gateway per zone you are controlling.

Lastly, you just have to puzzle out the syntax from their shitty rs232 manual.

Hope this helps.