Is there a way for me to know Alexa is listening without the LED?

 

For users who want an audible indication when Alexa is listening, you can turn on a “wake up sound”.  To do this, select MENU > SETTINGS > PREFERENCES > SOUND EFFECTS ON YOUR THERMOSTAT > ENABLE. Now a sound will play when you wake Alexa or when you finish speaking to Alexa on your ecobee4.