One of the biggest issue with touch screen phones is accidental clicking while phone in hands or in pocket, the issue is prominent on iPhone specially while on call, often accidentally hitting end button. To cure this annoyance here is an excellent Cydia app, Dialer Shield for jailbroken iPhones.
Dialer Shield as name suggests it shields from inadvertently triggering buttons during phone call. It does this by blocking all the buttons on call screen and placing another two way slider button for ending call or to unblock buttons.
The app is definitely worth a try if you suffering from accidental button press annoyance on your iPhone but it does cost you money. Dialer shield is paid app and available for $1.49 at BigBoss Cydia repository.