Time Check

This extension allows you to set alarms based on time of day, countdown, or events in Google Calendar.

Easily set alarms in Google Chrome based on countdown or time of day so you always show up on time. Choose from two alarm modes, two visual alerts, and five sounds. Now you can even set an alarm with a single click inside of Google Calendar! Time Check is free, easy to use, and makes a real difference in your ability to start and end every call and meeting on time.