I've been looking at the mdadm monitor, and thought it might be useful 
if it allowed extra context information (in the form of command line 
arguments) to be sent to the event program, so instead of just:

# mdadm -F /dev/md0 -p "md_event"

you could do something like:

# mdadm -F /dev/md0 -p "md_event -i <some_info>"

And the "-i <some_info>" will be passed on the command line to the event 
program. Of course you can usually figure out what the extra context 
should be in the event program itself, but it may take more work.

Here's a short patch (against mdadm 2.4) that does this.

Thanks,
Paul