Setting up a local RTMP Relay

Question

I'm trying to live stream an online game, but I lag, so what I'm trying to do is find a way to setup my live stream client which lets me specify a custom RTMP server to connect to another computer which I've setup and then have that computer relay the stream to another RTMP server.

Like this:

1. Main computer has the live stream client and main internet connection.
2. The main computer has the live stream client stream to an RTMP server on the secondary computer at 192.168.2.1
3. The secondary computer then takes the RTMP stream and redirects/relays/etc to another RTMP server using a different internet connection.

I have the part where the computers are all connected and using their own internet connections and such, but I need help setting up an RTMP relay server.

I tried the Flash Media Server thing but that was confusing as all hell.

The secondary computer is running Mac OS 10.6, but I could bootcamp Windows to run a Windows program for relaying the stream.

Anyone have any ideas?