iOS打开系统应用

• 电话

NSURL *url = [NSURL URLWithString:@"tel://18612345678"];
    if ([[UIApplication sharedApplication] canOpenURL:url]) {
        [[UIApplication sharedApplication] openURL:url];
    }

• 短信

@"tel://18612345678"

• 邮件

@"mailto:[email protected]"

• Facetime

@"facetime:[email protected]"

• iTunes

@"https://itunes.apple.com/cn/app/wei-xin/id414478124"

• 地图

@"http://maps.apple.com/?ll=114.06667,22.61667"

参考：
https://developer.apple.com/library/ios/featuredarticles/iPhoneURLScheme_Reference/Introduction/Introduction.html#/apple_ref/doc/uid/TP40007891-SW1