Yes, you need a smartphone or tablet to operate the Pluto Trigger. The compatible devices are iPhone 4s or later, iPad 3 or later, iPad Mini, iPod Touch 5 or later, Android 4.3 with Bluetooth 4.0 LE (Low Energy) or later. The Pluto Trigger app is used to adjust the settings and start one of the Modes on the trigger. Later on, some modes (e.g. Sound, Light, Lightning and PIR) are able to run stand-alone without a phone, even after a power cycle.