Like most smart light bulbs, the Playbulb is controlled via Bluetooth by an app on your phone. But rather than just having you push a button, the app takes advantage of your phone's accelerometer, so you can turn up or dim the lights simply by shaking it.
The Playbulb's role as a kind of justice-of-the-peace between light and sound gives you total, simultaneous, and automatic control of your environment. It reportedly allows you to fall asleep and/or wake up gradually using music or light instead of an alarm clock. Since you probably don't want crazy loud music blaring first thing in the morning, the size of the speaker doesn't handicap things.