LockDockBar is an application that allows you to launch your Phone, Mail, SMS and Calendar apps from your lock screen mode. You can get it on Cydia for free. When you install LockDockBar, it will automatically add the fixed icons to your lock screen such as Phone, Mail, SMS and Calender (it does not add an icon for the app to your SpringBoard). You can then launch and use any of the four application right from your lock screen. It also displays a badge on the icons (on the lock screen) indicating if you have any missed calls, texts and/or any new email. You can check out my post here on how to install LockDockBar via Cydia.