Source: http://gizmodo.com/5642656/jailbroken-iphones-can-surf-privately-with-free-cydia-app-covert
Porn-browsers with jailbroken iPhones who wish to keep their internet habits a secret (yes, it's a niche market, true), have been handed the free "Covert" tool on the Cydia app store, for use with the Mobile Safari browser.
Redmond Pie tried it out, describing that it works right in the Safari browser, with the "private browsing" activated when a new tab is opened. If surfers have forgotten whether they're browsing privately or not, they should simply try and remember that the UI turns gray when it's private. [Redmond Pie]