If you just want to give a notification, many people, myself included, just have a light change color. You can do that using the free IFTTT service) although lag varies from house to house), with Tasker on an android phone, or by using core.
If you have either Phillips hue lights or LIFX lights, both have their own IFTTT channels, so that’s probably the easiest method. At my house the lag is a pretty regular eight seconds, which works for some situations, but is a little long for others. But other people have much longer lag so you do need to investigate that.
