I deal a lot of multicast at work, and if you've ever tried managing a multicast network you'd understand the pain and complexity it takes to manage it. Not too long ago I came up with an EEM script to monitor a multicast stream, and to send a syslog notification if it ever drops below a certain threshold:
event manager applet eem-LoBW-MulticastSenderThis script monitors the multicast group X.X.X.X source Y.Y.Y.Y (with source subnet of Z.Z.Z.Z), and if the stream ever falls below 128000 bit/s (~100kbit/s), it will send a critical syslog message (you can easily substitute other actions to take instead of syslog messages here too; i.e. send an email, trap, TCL script, run CLI commands, etc).
event snmp oid 18.104.22.168.22.214.171.124.126.96.36.199.X.X.X.X.Y.Y.Y.Y.Z.Z.Z.Z get-type next entry-op lt entry-val 128000 entry-type increment poll-interval 10
action 1.0 syslog priority critical msg "Low bandwidth detected for the multicast group X.X.X.X source Y.Y.Y.Y (<100kbit/s)."
Can be very useful for proactive multicast monitoring if you understand the multicast application running through your network well enough to be able to set thresholds like above.
More to come with EEM....