XCDFakeCarrier.m

//
// Copyright (c) 2012-2013 Cédric Luthi / @0xced. All rights reserved.
//

#if TARGET_IPHONE_SIMULATOR

static const char *fakeCarrier;

#import <objc/runtime.h>

typedef struct {
	char itemIsEnabled[23];
	char timeString[64];
	int gsmSignalStrengthRaw;
	int gsmSignalStrengthBars;
	char serviceString[100];
	// ...
} StatusBarData;

typedef struct {
	char itemIsEnabled[24];
	char timeString[64];
	int gsmSignalStrengthRaw;
	int gsmSignalStrengthBars;
	char serviceString[100];
	// ...
} StatusBarData_6;

typedef struct {
	char itemIsEnabled[25];
	char timeString[64];
	int gsmSignalStrengthRaw;
	int gsmSignalStrengthBars;
	char serviceString[100];
	// ...
} StatusBarData_7;


@interface XCDFakeCarrier : NSObject
@end

@implementation XCDFakeCarrier

+ (void) load
{
	fakeCarrier = getenv("FAKE_CARRIER");
	if (!fakeCarrier)
	{
		NSLog(@"You must set the FAKE_CARRIER environment variable");
		return;
	}
	
	BOOL __block success = NO;
	Class UIStatusBarComposedData = objc_getClass("UIStatusBarComposedData");
	SEL selector = NSSelectorFromString(@"rawData");
	Method method = class_getInstanceMethod(UIStatusBarComposedData, selector);
	NSDictionary *statusBarDataInfo = @{ @"^{?=[23c][64c]ii[100c]": @"fake_rawData",
	                                     @"^{?=[24c][64c]ii[100c]": @"fake_rawData_6",
	                                     @"^{?=[25c][64c]ii[100c]": @"fake_rawData_7" };
	[statusBarDataInfo enumerateKeysAndObjectsUsingBlock:^(NSString *statusBarDataTypeEncoding, NSString *fakeSelectorString, BOOL *stop) {
		if (method && [@(method_getTypeEncoding(method)) hasPrefix:statusBarDataTypeEncoding])
		{
			SEL fakeSelector = NSSelectorFromString(fakeSelectorString);
			Method fakeMethod = class_getInstanceMethod(self, fakeSelector);
			success = class_addMethod(UIStatusBarComposedData, fakeSelector, method_getImplementation(fakeMethod), method_getTypeEncoding(fakeMethod));
			fakeMethod = class_getInstanceMethod(UIStatusBarComposedData, fakeSelector);
			method_exchangeImplementations(method, fakeMethod);
		}
	}];
	
	if (success)
		NSLog(@"Using \"%s\" fake carrier", fakeCarrier);
	else
		NSLog(@"XCDFakeCarrier failed to initialize");
}

- (StatusBarData *) fake_rawData
{
	StatusBarData *rawData = [self fake_rawData];
	strlcpy(rawData->serviceString, fakeCarrier, sizeof(rawData->serviceString));
	return rawData;
}

- (StatusBarData_6 *) fake_rawData_6
{
	StatusBarData_6 *rawData = [self fake_rawData_6];
	strlcpy(rawData->serviceString, fakeCarrier, sizeof(rawData->serviceString));
	return rawData;
}

- (StatusBarData_7 *) fake_rawData_7
{
	StatusBarData_7 *rawData = [self fake_rawData_7];
	strlcpy(rawData->serviceString, fakeCarrier, sizeof(rawData->serviceString));
	return rawData;
}

@end

#endif

Hi, This is awesome, but I can't figure out how to display the cellular bar strength and eliminate the WiFi icon. Anyone have insight? Thanks!

See my fork: https://gist.github.com/ksuther/8211001

On iOS 7, you can set itemIsEnabled[3] to 1, gsmSignalStrengthBars to 5, and then set dataNetworkType to one of the following:

0 - GPRS
1 - E (EDGE)
2 - 3G
3 - 4G
4 - LTE
5 - Wi-Fi
6 - Personal Hotspot
7 - 1x
8 - Blank

To set dataNetworkType you'll need to fill out more of the struct from this header: https://github.com/nst/iOS-Runtime-Headers/blob/master/Frameworks/UIKit.framework/UIStatusBarComposedData.h