Yes! This a new feature in Reflector Teacher.
There are two ways to begin and end a voice-over recording.
You can select the microphone icon in your Reflector Teacher menu. The drop down arrow beside this icon will let you choose which microphone you will record from. This must be a microphone that is attached to your computer.
You can use also use key commands to begin and end a voice-over.
Press Command + Shift + V to begin or end recording voice-over audio.