From Xojo Documentation
If true, the device is near the user.
The ProximityMonitoringEnabled property must be True for this property to return accurate information. To preserver battery power, only set ProximityMonitoringEnabled to True while calling IsProximityNear and then set it to False as soon as you no longer need it.
If the device is near the user, display a message:
If System.Device.IsProximityNear Then
MessageBox("The device is close to you.")