BounceTerm may be just what you're looking for. From the web page:
BounceTerm is a SIMBL plugin for Mac OS X's Terminal.app that makes the dock icon bounce when a bell or beep is triggered. This can be useful if you have a long-running process going on and you want to be notified when it's done (assuming it beeps, of course).
No configuration is necessary, just open the .dmg file, run Install, and restart Terminal.app. To uninstall, simply run Uninstall from the .dmg.
If you want to make sure the plugin's working, try running
while [ 1 ]; do echo -n '\a'; sleep 2; done
in your shell and focusing a window in another application. You should see Terminal.app's dock icon bounce every two seconds.
So for your scenario:
a && b && c && while [ 1 ]; do echo -n '\a'; sleep 2; done