Allow the developer to know on which harware the program runs (iPhone4, iPhone4S, iPhone5, etc...).

UIDevice-Hardware.h

/*
 Erica Sadun, http://ericasadun.com
 iPhone Developer's Cookbook, 5.0 Edition
 BSD License, Use at your own risk
 */

#import <UIKit/UIKit.h>

#define IFPGA_NAMESTRING @"iFPGA"

#define IPHONE_1G_NAMESTRING @"iPhone 1G"
#define IPHONE_3G_NAMESTRING @"iPhone 3G"
#define IPHONE_3GS_NAMESTRING @"iPhone 3GS"
#define IPHONE_4_NAMESTRING @"iPhone 4"
#define IPHONE_4S_NAMESTRING @"iPhone 4S"
#define IPHONE_5_NAMESTRING @"iPhone 5"
#define IPHONE_UNKNOWN_NAMESTRING @"Unknown iPhone"

#define IPOD_1G_NAMESTRING @"iPod touch 1G"
#define IPOD_2G_NAMESTRING @"iPod touch 2G"
#define IPOD_3G_NAMESTRING @"iPod touch 3G"
#define IPOD_4G_NAMESTRING @"iPod touch 4G"
#define IPOD_UNKNOWN_NAMESTRING @"Unknown iPod"

#define IPAD_1G_NAMESTRING @"iPad (First Generation)"
#define IPAD_2G_NAMESTRING @"iPad 2"
#define IPAD_3G_NAMESTRING @"New iPad"
#define IPAD_UNKNOWN_NAMESTRING @"Unknown iPad"

#define APPLETV_2G_NAMESTRING @"Apple TV 2G"
#define APPLETV_UNKNOWN_NAMESTRING @"Unknown Apple TV"

#define IOS_FAMILY_UNKNOWN_DEVICE @"Unknown iOS device"

#define SIMULATOR_NAMESTRING @"iPhone Simulator"
#define SIMULATOR_IPHONE_NAMESTRING @"iPhone Simulator"
#define SIMULATOR_IPAD_NAMESTRING @"iPad Simulator"

typedef enum {
  UIDeviceUnknown,
  
  UIDeviceSimulator,
  UIDeviceSimulatoriPhone,
  UIDeviceSimulatoriPad,
  
  UIDevice1GiPhone,
  UIDevice3GiPhone,
  UIDevice3GSiPhone,
  UIDevice4iPhone,
  UIDevice4SiPhone,
  UIDevice5iPhone,
  
  UIDevice1GiPod,
  UIDevice2GiPod,
  UIDevice3GiPod,
  UIDevice4GiPod,
  
  UIDevice1GiPad,
  UIDevice2GiPad,
  UIDevice3GiPad,
  
  UIDeviceAppleTV2,
  UIDeviceUnknownAppleTV,
  
  UIDeviceUnknowniPhone,
  UIDeviceUnknowniPod,
  UIDeviceUnknowniPad,
  UIDeviceIFPGA,
  
} UIDevicePlatform;

@interface UIDevice (Hardware)
- (NSString *) platform;
- (NSString *) hwmodel;
- (NSUInteger) platformType;
- (NSString *) platformString;

- (NSUInteger) cpuFrequency;
- (NSUInteger) busFrequency;
- (NSUInteger) totalMemory;
- (NSUInteger) userMemory;

- (NSNumber *) totalDiskSpace;
- (NSNumber *) freeDiskSpace;

- (NSString *) macaddress;
@end

UIDevice-Hardware.m

/*
 Erica Sadun, http://ericasadun.com
 iPhone Developer's Cookbook, 5.0 Edition
 BSD License, Use at your own risk
 */

// Thanks to Emanuele Vulcano, Kevin Ballard/Eridius, Ryandjohnson, Matt Brown, etc.

#include <sys/socket.h> // Per msqr
#include <sys/sysctl.h>
#include <net/if.h>
#include <net/if_dl.h>

#import "UIDevice-Hardware.h"

@implementation UIDevice (Hardware)
/*
 Platforms
 iFPGA -> ??
 
 iPhone1,1 -> iPhone 1G, M68
 iPhone1,2 -> iPhone 3G, N82
 iPhone2,1 -> iPhone 3GS, N88
 iPhone3,1 -> iPhone 4/AT&T, N89
 iPhone3,2 -> iPhone 4/Other Carrier?, ??
 iPhone3,3 -> iPhone 4/Verizon, TBD
 iPhone4,1 -> (iPhone 5/AT&T), TBD
 iPhone4,2 -> (iPhone 5/Verizon), TBD
 
 iPod1,1 -> iPod touch 1G, N45
 iPod2,1 -> iPod touch 2G, N72
 iPod2,2 -> Unknown, ??
 iPod3,1 -> iPod touch 3G, N18
 iPod4,1 -> iPod touch 4G, N80
 // Thanks NSForge
 iPad1,1 -> iPad 1G, WiFi and 3G, K48
 iPad2,1 -> iPad 2G, WiFi, K93
 iPad2,2 -> iPad 2G, GSM 3G, K94
 iPad2,3 -> iPad 2G, CDMA 3G, K95
 iPad3,1 -> (iPad 3G, GSM)
 iPad3,2 -> (iPad 3G, CDMA)
 
 AppleTV2,1 -> AppleTV 2, K66
 
 i386, x86_64 -> iPhone Simulator
 */


#pragma mark sysctlbyname utils
- (NSString *) getSysInfoByName:(char *)typeSpecifier
{
  size_t size;
  sysctlbyname(typeSpecifier, NULL, &size, NULL, 0);
  
  char *answer = malloc(size);
  sysctlbyname(typeSpecifier, answer, &size, NULL, 0);
  
  NSString *results = [NSString stringWithCString:answer encoding: NSUTF8StringEncoding];
  
  free(answer);
  return results;
}

- (NSString *) platform
{
  return [self getSysInfoByName:"hw.machine"];
}


// Thanks, Tom Harrington (Atomicbird)
- (NSString *) hwmodel
{
  return [self getSysInfoByName:"hw.model"];
}

#pragma mark sysctl utils
- (NSUInteger) getSysInfo: (uint) typeSpecifier
{
  size_t size = sizeof(int);
  int results;
  int mib[2] = {CTL_HW, typeSpecifier};
  sysctl(mib, 2, &results, &size, NULL, 0);
  return (NSUInteger) results;
}

- (NSUInteger) cpuFrequency
{
  return [self getSysInfo:HW_CPU_FREQ];
}

- (NSUInteger) busFrequency
{
  return [self getSysInfo:HW_BUS_FREQ];
}

- (NSUInteger) totalMemory
{
  return [self getSysInfo:HW_PHYSMEM];
}

- (NSUInteger) userMemory
{
  return [self getSysInfo:HW_USERMEM];
}

- (NSUInteger) maxSocketBufferSize
{
  return [self getSysInfo:KIPC_MAXSOCKBUF];
}

#pragma mark file system -- Thanks Joachim Bean!
- (NSNumber *) totalDiskSpace
{
  NSDictionary *fattributes = [[NSFileManager defaultManager] attributesOfFileSystemForPath:NSHomeDirectory() error:nil];
  return [fattributes objectForKey:NSFileSystemSize];
}

- (NSNumber *) freeDiskSpace
{
  NSDictionary *fattributes = [[NSFileManager defaultManager] attributesOfFileSystemForPath:NSHomeDirectory() error:nil];
  return [fattributes objectForKey:NSFileSystemFreeSize];
}

#pragma mark platform type and name utils
- (NSUInteger) platformType
{
  NSString *platform = [self platform];
  
  // The ever mysterious iFPGA
  if ([platform isEqualToString:@"iFPGA"]) return UIDeviceIFPGA;
  
  // iPhone
  if ([platform isEqualToString:@"iPhone1,1"]) return UIDevice1GiPhone;
  if ([platform isEqualToString:@"iPhone1,2"]) return UIDevice3GiPhone;
  if ([platform hasPrefix:@"iPhone2"]) return UIDevice3GSiPhone;
  if ([platform hasPrefix:@"iPhone3"]) return UIDevice4iPhone;
  if ([platform hasPrefix:@"iPhone4"]) return UIDevice4SiPhone;
  if ([platform hasPrefix:@"iPhone5"]) return UIDevice5iPhone;
  
  // iPod
  if ([platform hasPrefix:@"iPod1"]) return UIDevice1GiPod;
  if ([platform hasPrefix:@"iPod2"]) return UIDevice2GiPod;
  if ([platform hasPrefix:@"iPod3"]) return UIDevice3GiPod;
  if ([platform hasPrefix:@"iPod4"]) return UIDevice4GiPod;
  
  // iPad
  if ([platform hasPrefix:@"iPad1"]) return UIDevice1GiPad;
  if ([platform hasPrefix:@"iPad2"]) return UIDevice2GiPad;
  if ([platform hasPrefix:@"iPad3"]) return UIDevice3GiPad;
  
  // Apple TV
  if ([platform hasPrefix:@"AppleTV2"]) return UIDeviceAppleTV2;
  
  if ([platform hasPrefix:@"iPhone"]) return UIDeviceUnknowniPhone;
  if ([platform hasPrefix:@"iPod"]) return UIDeviceUnknowniPod;
  if ([platform hasPrefix:@"iPad"]) return UIDeviceUnknowniPad;
  
  // Simulator thanks Jordan Breeding
  if ([platform hasSuffix:@"86"] || [platform isEqual:@"x86_64"])
  {
    BOOL smallerScreen = [[UIScreen mainScreen] bounds].size.width < 768;
    return smallerScreen ? UIDeviceSimulatoriPhone : UIDeviceSimulatoriPad;
  }
  
  return UIDeviceUnknown;
}

- (NSString *) platformString
{
  switch ([self platformType])
  {
    case UIDevice1GiPhone: return IPHONE_1G_NAMESTRING;
    case UIDevice3GiPhone: return IPHONE_3G_NAMESTRING;
    case UIDevice3GSiPhone: return IPHONE_3GS_NAMESTRING;
    case UIDevice4iPhone: return IPHONE_4_NAMESTRING;
    case UIDevice4SiPhone: return IPHONE_4S_NAMESTRING;
    case UIDevice5iPhone: return IPHONE_5_NAMESTRING;
    case UIDeviceUnknowniPhone: return IPHONE_UNKNOWN_NAMESTRING;
      
    case UIDevice1GiPod: return IPOD_1G_NAMESTRING;
    case UIDevice2GiPod: return IPOD_2G_NAMESTRING;
    case UIDevice3GiPod: return IPOD_3G_NAMESTRING;
    case UIDevice4GiPod: return IPOD_4G_NAMESTRING;
    case UIDeviceUnknowniPod: return IPOD_UNKNOWN_NAMESTRING;
      
    case UIDevice1GiPad : return IPAD_1G_NAMESTRING;
    case UIDevice2GiPad : return IPAD_2G_NAMESTRING;
    case UIDevice3GiPad : return IPAD_3G_NAMESTRING;
    case UIDeviceUnknowniPad : return IPAD_UNKNOWN_NAMESTRING;
      
    case UIDeviceAppleTV2 : return APPLETV_2G_NAMESTRING;
    case UIDeviceUnknownAppleTV: return APPLETV_UNKNOWN_NAMESTRING;
      
    case UIDeviceSimulator: return SIMULATOR_NAMESTRING;
    case UIDeviceSimulatoriPhone: return SIMULATOR_IPHONE_NAMESTRING;
    case UIDeviceSimulatoriPad: return SIMULATOR_IPAD_NAMESTRING;
      
    case UIDeviceIFPGA: return IFPGA_NAMESTRING;
      
    default: return IOS_FAMILY_UNKNOWN_DEVICE;
  }
}

#pragma mark MAC addy
// Return the local MAC addy
// Courtesy of FreeBSD hackers email list
// Accidentally munged during previous update. Fixed thanks to mlamb.
- (NSString *) macaddress
{
  int mib[6];
  size_t len;
  char *buf;
  unsigned char *ptr;
  struct if_msghdr *ifm;
  struct sockaddr_dl *sdl;
  
  mib[0] = CTL_NET;
  mib[1] = AF_ROUTE;
  mib[2] = 0;
  mib[3] = AF_LINK;
  mib[4] = NET_RT_IFLIST;
  
  if ((mib[5] = if_nametoindex("en0")) == 0) {
    printf("Error: if_nametoindex error\n");
    return NULL;
  }
  
  if (sysctl(mib, 6, NULL, &len, NULL, 0) < 0) {
    printf("Error: sysctl, take 1\n");
    return NULL;
  }
  
  if ((buf = malloc(len)) == NULL) {
    printf("Could not allocate memory. error!\n");
    return NULL;
  }
  
  if (sysctl(mib, 6, buf, &len, NULL, 0) < 0) {
    printf("Error: sysctl, take 2");
    if (buf!=NULL) {
      free(buf);
    }
    return NULL;
  }
  
  ifm = (struct if_msghdr *)buf;
  sdl = (struct sockaddr_dl *)(ifm + 1);
  ptr = (unsigned char *)LLADDR(sdl);
  NSString *outstring = [NSString stringWithFormat:@"%02X:%02X:%02X:%02X:%02X:%02X",
                         *ptr, *(ptr+1), *(ptr+2), *(ptr+3), *(ptr+4), *(ptr+5)];
  // NSString *outstring = [NSString stringWithFormat:@"%02X%02X%02X%02X%02X%02X",
  // *ptr, *(ptr+1), *(ptr+2), *(ptr+3), *(ptr+4), *(ptr+5)];
  free(buf);
  
  return outstring;
}

// Illicit Bluetooth check -- cannot be used in App Store
/*
 Class btclass = NSClassFromString(@"GKBluetoothSupport");
 if ([btclass respondsToSelector:@selector(bluetoothStatus)])
 {
 printf("BTStatus %d\n", ((int)[btclass performSelector:@selector(bluetoothStatus)] & 1) != 0);
 bluetooth = ((int)[btclass performSelector:@selector(bluetoothStatus)] & 1) != 0;
 printf("Bluetooth %s enabled\n", bluetooth ? "is" : "isn't");
 }
 */
@end