A method includes running an application on a mobile computing device, the mobile computing device accepting biometric input, and the mobile computing device enabling one or more function of the application only in response to the biometric input indicating that more than one person is present in the same location. Examples of suitable biometric input include a fingerprint, heartbeat, iris scan, facial recognition, and voice recognition. The biometric input may be provided directly to the mobile computing device from the more than one person present, or the biometric input may be provided by a first person to a first mobile computing device and by a second person to a second mobile computing device.