I'm a 100% open source guy, for my own use anyway. Wireshark shows all traffic on a segment, the source and destination, ports, what protocol etc. I assume this app you mention is similar?
There's a really nifty graphic mapper called etherape, but it's less useful ultimately because you can't save any of it's output.
The real conversation piece is driftnet. Sit in a wifi hot spot and sniff images out of the traffic, you literally see the images other people are seeing in their browsers. (certain file formats anyway)
I strike up conversations with folk at wifi hot spots about their computers and security. When I show them pictures (on MY screen) that they were just looking at on theirs they have a tendency to listen. =)
Not sure if there are win32 versions. I think there may be, and I'd guess they'd be open source also.
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