Thanks in advance.
I got the information about the iphone sensors from http://ipod.about.com/od/ipodiphonehardwareterms/qt/iphone-sensors.htm. But I didn\'t get info
It is possible, and the framework is public.
You can activate the connection to the sensor like so :
[[UIDevice currentDevice] setProximityMonitoringEnabled:YES];
BTW, it doesn't seem to be using the light sensor, because proximity sensing would tweak out in a dark room.
However, the API call basically blanks the screen when you hold the phone up to your face. Not useful for interaction, sadly.
Here is a guide about iPhone sensors : iPhone sensors