更新了一下，支持iPhone4和iPad，iPod Touch4

#import <Foundation/Foundation.h>
#import <sys/utsname.h>

enum {
    MODEL_UNKNOWN,
    MODEL_IPHONE_SIMULATOR,
    MODEL_IPOD_TOUCH,
    MODEL_IPOD_TOUCH_2G,
    MODEL_IPOD_TOUCH_3G,
    MODEL_IPOD_TOUCH_4G,
    MODEL_IPHONE,
    MODEL_IPHONE_3G,
    MODEL_IPHONE_3GS,
    MODEL_IPHONE_4G,
    MODEL_IPAD
};

@interface DeviceDetection : NSObject

+ (uint) detectDevice;
+ (int) detectModel;

+ (NSString *) returnDeviceName:(BOOL)ignoreSimulator;
+ (BOOL) isIPodTouch;
+ (BOOL) isOS4;
+ (BOOL) canSendSms;

@end

#import "DeviceDetection.h"
#import <MessageUI/MessageUI.h>
#include <sys/types.h>
#include <sys/sysctl.h>

@implementation DeviceDetection

+ (BOOL) isIPodTouch
{
    int model = [DeviceDetection detectDevice];
    if (model == MODEL_IPOD_TOUCH || model == MODEL_IPAD){
        //|| model == MODEL_IPHONE_SIMULATOR){
        return YES;
    }    
    else {
        return NO;
    }

}

+ (BOOL) isOS4
{
    // TBD
    
    return YES;
    
}

+ (BOOL)canSendSms
{
    return [MFMessageComposeViewController canSendText];
}

+ (NSString *)platform{
    size_t size;
    sysctlbyname("hw.machine", NULL, &size, NULL, 0);
    char *machine = malloc(size);
    sysctlbyname("hw.machine", machine, &size, NULL, 0);
    NSString *platform = [NSString stringWithUTF8String:machine];
    free(machine);
    return platform;
}

+ (int) detectModel{
    NSString *platform = [DeviceDetection platform];
    
    if ([platform isEqualToString:@"iPhone1,1"])   
        return MODEL_IPHONE;
    
    if ([platform isEqualToString:@"iPhone1,2"])   
        return MODEL_IPHONE_3G;
    
    if ([platform isEqualToString:@"iPhone2,1"])
        return MODEL_IPHONE_3GS;
    
    if ([platform isEqualToString:@"iPhone3,1"])    
        return MODEL_IPHONE_4G;
    
    if ([platform isEqualToString:@"iPod1,1"])      
        return MODEL_IPOD_TOUCH;
    
    if ([platform isEqualToString:@"iPod2,1"])      
        return MODEL_IPOD_TOUCH_2G;
    
    if ([platform isEqualToString:@"iPod3,1"])      
        return MODEL_IPOD_TOUCH_3G;
    
    if ([platform isEqualToString:@"iPod4,1"])      
        return MODEL_IPOD_TOUCH_4G;
    
    if ([platform isEqualToString:@"iPad1,1"])      
        return MODEL_IPAD;
    
    if ([platform isEqualToString:@"i386"])         
        return MODEL_IPHONE_SIMULATOR;
    
    return MODEL_UNKNOWN;
}

+ (uint) detectDevice {
    NSString *model= [[UIDevice currentDevice] model];
    
    // Some iPod Touch return "iPod Touch", others just "iPod"
    
    NSString *iPodTouch = @"iPod Touch";
    NSString *iPodTouchLowerCase = @"iPod touch";
    NSString *iPodTouchShort = @"iPod";
    NSString *iPad = @"iPad";
    
    NSString *iPhoneSimulator = @"iPhone Simulator";
    
    uint detected;
    
    if ([model compare:iPhoneSimulator] == NSOrderedSame) {
        // iPhone simulator
        detected = MODEL_IPHONE_SIMULATOR;
    }
    else if ([model compare:iPad] == NSOrderedSame) {
        // iPad
        detected = MODEL_IPAD;
    } else if ([model compare:iPodTouch] == NSOrderedSame) {
        // iPod Touch
        detected = MODEL_IPOD_TOUCH;
    } else if ([model compare:iPodTouchLowerCase] == NSOrderedSame) {
        // iPod Touch
        detected = MODEL_IPOD_TOUCH;
    } else if ([model compare:iPodTouchShort] == NSOrderedSame) {
        // iPod Touch
        detected = MODEL_IPOD_TOUCH;
    } else {
        // Could be an iPhone V1 or iPhone 3G (model should be "iPhone")
        struct utsname u;
       
        // u.machine could be "i386" for the simulator, "iPod1,1" on iPod Touch, "iPhone1,1" on iPhone V1 & "iPhone1,2" on iPhone3G
       
        uname(&u);
       
        if (!strcmp(u.machine, "iPhone1,1")) {
            detected = MODEL_IPHONE;
        } else if (!strcmp(u.machine, "iPhone1,2")){
            detected = MODEL_IPHONE_3G;
        } else if (!strcmp(u.machine, "iPhone2,1")){
            detected = MODEL_IPHONE_3GS;
        } else if (!strcmp(u.machine, "iPhone3,1")){
            detected = MODEL_IPHONE_4G;
        }
    }
    return detected;
}

+ (NSString *) returnDeviceName:(BOOL)ignoreSimulator {
    NSString *returnValue = @"Unknown";
    
    switch ([DeviceDetection detectDevice]) {
        case MODEL_IPHONE_SIMULATOR:
            if (ignoreSimulator) {
                returnValue = @"iPhone 3G";
            } else {
                returnValue = @"iPhone Simulator";
            }
            break;
        case MODEL_IPOD_TOUCH:
            returnValue = @"iPod Touch";
            break;
        case MODEL_IPHONE:
            returnValue = @"iPhone";
            break;
        case MODEL_IPHONE_3G:
            returnValue = @"iPhone 3G";
            break;
        default:
            break;
    }
    
    return returnValue;
}

@end