A notification center notification would be ideal but growl, bounce dock, sound, etc would be fine, too (or if this can only be done in Terminal.app I\'d be willing to switc
There is an OSS tool called noti.
You can easily install it with brew install noti and start using it just by prefixing your command with noti like noti sleep 3.
brew install noti
noti
noti sleep 3