This would be a handy to have a beep once FreeNAS has completely booted. I can't imagine it would be difficult to add and as Bohs mentioned, diagnostic beeps for drive failures as an example would be great as well, maybe the sequence would be "beep" for drive ada0, "beep beep" for drive ada1 and so on and maybe when we hit 2 digits, two separate beeps like 14 would be 1 beep followed by 4 beeps. It could be more elaborate depending on all the possible errors you might want to be notified. Maybe a sequence tones to indicate catastrophic failure. The list could go on. One thing that should be there is we get the beeps back is a disable beep feature.
Hey this is a feature wish list so why not wish for everything.