Use the following API to enable/disable the proximity sensor.
[UIDevice currentDevice].proximityMonitoringEnabled = NO; // Disables the Proximity Sensor
[UIDevice currentDevice].proximityMonitoringEnabled = YES; // Enables the Proximity Sensor
Not all iOS devices have proximity sensors. To determine if proximity monitoring is available, attempt to enable it. If the value of the proximityMonitoringEnabled property remains NO, proximity monitoring is not available.