Detect the specific iPhone/iPod touch model

Most complete UIDevice (Hardware) category probably is http://github.com/erica/uidevice-extension/ (by Erica Sadun):

[[UIDevice currentDevice] platformType]   // ex: UIDevice4GiPhone
[[UIDevice currentDevice] platformString] // ex: @"iPhone 4G"

You can get the device model number using uname from sys/utsname.h. For example:

#import <sys/utsname.h>

NSString*
machineName()
{
    struct utsname systemInfo;
    uname(&systemInfo);

    return [NSString stringWithCString:systemInfo.machine
                              encoding:NSUTF8StringEncoding];
}

The result should be:

@"i386"      on the simulator
@"iPod1,1"   on iPod Touch
@"iPod2,1"   on iPod Touch Second Generation
@"iPod3,1"   on iPod Touch Third Generation
@"iPod4,1"   on iPod Touch Fourth Generation
@"iPhone1,1" on iPhone
@"iPhone1,2" on iPhone 3G
@"iPhone2,1" on iPhone 3GS
@"iPad1,1"   on iPad
@"iPad2,1"   on iPad 2
@"iPad3,1"   on iPad 3 (aka new iPad)
@"iPhone3,1" on iPhone 4
@"iPhone4,1" on iPhone 4S
@"iPhone5,1" on iPhone 5
@"iPhone5,2" on iPhone 5