Are Visual Alerts Possible?

I connected my iMac's headphone jack to my home stereo for better audio. Of course, that mutes the iMac's speakers and if I forget to turn on my stereo, I won't hear alert beeps when I click on something that won't work. I don't want to necessarily listen through my stereo system all the time; only when watching DVDs or music videos on youtube, etc.

Is there a program that adds a visual indicator to the Mac's alert beeps? I imagine there must be something for hearing impaired users.

Thanks!