Tool for bus sniffing and direction detection?

[agehall]

I need help figuring out what kind of tool I'm looking for - googling words like "monitor", "bus" and "driver" doesn't really give relevant results...

My problem is that I have a bus that consists of three wires, CLK, SDA and SRQ. I want to sniff the traffic but I also want to detect the direction of it as either side can be driving things. I'm far from an expert, but I don't see any way of accomplishing this with a simple logic analyzer.

Surely there must be a piece of ready-made hardware that can do this? I'm looking for something cheap and we are talking low speed here, way under 1Mhz.

If there isn't a ready-made tool for this sort of thing, my backup plan is to cut the three lines I want to monitor and toss an Arduino inbetween so that I can detect incoming data from both ends and pass it to the other side.

Any suggestions for how to do this?

[HackedFridgeMagnet]

Bus Pirate is open source, so you could tweak it to fit your needs.