serial sniffing

Hi,

I am looking for something on par with windows' PortMon to log the data, 
the various settings and control triggers of a serial port communication 
on Mac OS X, using a keyspan usb-serial adapter.
Having googled the question over and over again, I am at a loss...

I did not any helpful docs on Apple web site, so I a turning to you, 
darwin guys....

Can you tell me how I could sniff a serial port ?
How could I write a kext to do my own serial drivers ?
do you have any docs on th e matter.

Thanks in advance,
--Philippe