You can definitely set it to stay on after it detects motion (there is a "do nothing" setting in the Hue app for that). There is not a button on the sensor that you can use to turn off the light; however you can buy a separate Hue Dimmer Switch to place on your wall or around your home to control the lights via button press. I have two of those, and they work great!
Philips - Hue Wireless Dimmer Switch with Remote - White
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