OSX PushToTalk mutes and unmutes the microphone via keypress.
When the Application starts, it will add a status icon. Hold the Right option key to talk, and release to mute
The icon indicator will be translucent if the microphone is muted.
Application Installer (dmg) can be downloaded in the Release Section
I did not sign the App. To enable exception for this app follow https://support.apple.com/kb/PH11436?locale=en_US
If you want to be sure, just compile the project, Archive & export PushToTalk.app