Works well, but it requires a bit more setup.
- In Time Master, make sure "Audible Notifications" is set to X minutes, and also "Alert & Vibrate" is checked.
- In the Settings app, navigate to Notifications->Time Master, and make sure "Sounds" is enabled (this needs to be on even for vibrate. If the phone is muted, then it will only vibrate). You can optionally enable displaying an alert on the home screen if the device is locked from that screen too.