As suggested by the title with SlideAnswer you can answer or reject incoming calls with a slide to the right or the left. This will prevent errors which, as you know well, with the touchscreen display are quite frequent.
SlideAnswer is available for all devices Symbian ^ 3 and S60 5th Edition . The installer can be downloaded by clicking the links below or by accessing this page of Ovi Store.
At a cost of 2 Euro, however, you can buy SlideAnswer Pro , which enables autorun allows, through a slide, access to the taskmanager or main menu.