LineIn is a simple application for OS X to enable the soft playthru of audio from input devices. In simpler terms, you can use LineIn to play sound coming in through a microphone or any other device plugged in to your Sound In port, just as was once available with OS 9's "Play input through output device" option.
What is new in this release:
A long-standing issue with latency in LineIn has finally been cured! We've also added a menu item for toggling play-thru.