Disclosed is a mobile device to authenticate a user. The mobile device may comprise: a first sensor; a second sensor to use more power than the first sensor; and a processor coupled to the first sensor and the second sensor. The processor may be configured to: collect data from the first sensor; determine if an environmental change occurred based on the collected data from the first sensor; engage the second sensor to collect data if the environmental change occurred; and modify a polling rate for the second sensor based on the collected data from the second sensor.