Cydia app xCon to Bypass Jailbreak Detection. But not all apps can be bypassed
xCon is available free of charge in Cydia. No configuration is needed; just install and go.
page below shows what apps can be bypassed
http://theiphonewiki.com/wiki/XCon
Recently, a sizable handful of applications in Apple's own App Store have been implementing procedures to check the authenticity of the device on which the app itself is running, forbidding or inhibiting usage of certain features or even the app altogether. Obvious reasons are about the innate security risks of jailbreaking your device (e.g. banking companies don't want the blame for some rogue keylogger disguised as a tweak snagging your account info). However, most of the time, it seems as if companies are worried about the possibility of tweaks bypassing certain restrictions implemented into their apps. Video streaming apps are notorious for this; the companies don't want users bypassing restrictions on when and where you can stream their content, so instead of doing the responsible thing and obfuscating their restriction attempts, they instead block all jailbroken devices, regardless of malicious intent or lack thereof.
Cheers
Rescue PC