I need to get infos about the nearest cell towers (something like the cell id). To identify a place without consuming power, by making a list of possible cells if for example.
I looked at the coretelephony framework but did not see anything about the cell towers. Is there another way to acces this ? Or is this only possible with private API call ?
In iOS 4.0 there is a startMonitoringSignificantLocationChanges delegate API in CoreLocation that only uses cellular information. You don't get the actual tower information, but you don't need it if you'd only be using it to extrapolate a lat/lon coordinate in any case.
See also the Location Awareness Programming Guide
The significant-change location service offers a low-power location service for devices with cellular radios. This service is available only in iOS 4.0 and later and can also wake up an application that is suspended or not running. (The significant-change location service drastically reduces battery drain by monitoring only cell tower changes, but the service works only on devices with cellular radios.)