Talk Toggle is described as 'Mute your microphone with a customizable shortcut'. There are seven alternatives to Talk Toggle for Mac and Windows. The best alternative is AHK MicMute, which is both free and Open Source. Other great apps like Talk Toggle are MicSwitch (Free, Open Source), Shush (Paid), Mic Drop (Paid) and MuteMyMic (Free).
MicSwitch allows you to mute/unmute your system microphone using a predefined system-wide hotkey which will affect any program that uses the microphone (no more heavy breathing during Skype conferences, hooray!).