Extended Networking cydia tweak allows you to control almost every outgoing and incoming connections to your device.
You can block the connection to certain URLs (named “Custom Block” in preferences), that contains your given string. Custom Block is almost system wide blocker.
The tweak has got a custom built-in block system that only blocks connection on WebView based apps and Safari, this is used to block connection to AD sites (built in blacklist with thousands of hosts), or to block content/pages that you don’t want to see on your browser (for example blocking adult sites).
You can protect yourself from being redirected to AppStore or any other apps. A polite popup will appear to ask you to allow the browser to redirect you. Extended Networking comes with a Notification Center widget to monitor the cellular (EDGE, 3G, LTE) usage of your device. You can set a turn date, when the counter resets, and the limit of your data plan, what you can set in different units. Moreover you can turn on Push Notifications to always know when you are close to your limit. There is a useful section for developers where they can monitor the outgoing connection (including HTTP headers) from certain system classes (NSURLConnection, NSURLSession, NSURLRequest, UIWebView) in system logs (check iphonedevwiki for more info about how to watch syslogs).
To turn on the notification center widget: iOS 8: Enable it directly in Notification Center
Configure options from Settings.