I use GeekTool to display some network information for my MacBook on my desktop. One thing I couldn't find was a way to show the current transfer rate (in Kb/sec) in and out. So I wrote a shell script that calls on netstat, waits one second, calls on netstat again, and then uses the difference in the numbers to display how many kilobytes were sent or received during that second.
If you use ethernet instead of AirPort, you'll have to change en1 to the interface you need (probably en0). This could also be used to monitor your bluetooth speeds as well. To set this up, first create a file (I named mine inout.sh) and save it wherever you like. Insert the following code and save it:
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