The developer of tweaks and applications for Cydia known as moeseth finished his Tweak Week today by releasing the Hidden Call Log tweak. This tweak has the role of hiding the list of calls received/made by us using an iPhone terminal and this function was implemented with the help of a new button available in the Phone application. By pressing that button we can hide all the calls from our call list so that no one knows how and with whom we spoke.
In iOS 5, Apple implemented possibility to delete individual calls from the call list, so maybe you don't need Hidden Call Log for now. The tweak is not yet available in Cydia but will probably be released by tomorrow.
