A simple static class to output semi-accurate memory usage and free memory during runtime.

MemoryManager.h

//
//  MemoryManager.h
//
//  Created by Shilo White on 3/12/12.
//  Copyright (c) 2012 Shilocity Productions. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface MemoryManager : NSObject
+ (uint)memoryUsageBytes;
+ (float)memoryUsageMegabytes;
+ (uint)memoryFreeBytes;
+ (float)memoryFreeMegabytes;
@end

MemoryManager.m

//
//  MemoryManager.m
//
//  Created by Shilo White on 3/12/12.
//  Copyright (c) 2012 Shilocity Productions. All rights reserved.
//

#import "MemoryManager.h"
#import <mach/mach.h>
#import <mach/mach_host.h>

@implementation MemoryManager
+ (uint)memoryUsageBytes {
	struct task_basic_info info;
	mach_msg_type_number_t size = sizeof(info);
	kern_return_t kerr = task_info(mach_task_self(), TASK_BASIC_INFO, (task_info_t)&info, &size);
    return (kerr == KERN_SUCCESS)?info.resident_size:0;
}

+ (float)memoryUsageMegabytes {
    return (float)[self memoryUsageBytes]/1048576.0f;
}

+ (uint)memoryFreeBytes {
	mach_port_t host_port;
	mach_msg_type_number_t host_size;
	vm_size_t pagesize;
	host_port = mach_host_self();
	host_size = sizeof(vm_statistics_data_t) / sizeof(integer_t);
	host_page_size(host_port, &pagesize);
	vm_statistics_data_t vm_stat;
	if (host_statistics(host_port, HOST_VM_INFO, (host_info_t)&vm_stat, &host_size) != KERN_SUCCESS) return 0;
	natural_t mem_free = vm_stat.free_count * pagesize;
	return mem_free;
}

+ (float)memoryFreeMegabytes {
    return (float)[self memoryFreeBytes]/1048576.0f;
}
@end