LockInfo is another of those must have tweak on your jailbroken iPhone and iPad.

The tweak, that has just been recently updated to version 4.0.4.9, allows you to customize the lockscreen of your device with all the information you need the most. The tweak also supports plugins such as Mail, Calendar, Reminders, SMS, Push Notifications, etc, to expand the amount of info you can have displayed on your lockscreen.
After installation the tweak can be configured through the Settings app on your device.

The tweak has some really nice features: the theme of LockInfo is fully customizable, there is a Favorite plugin that will let you call anyone from your favorite list, and you can also lock one section of the screen and scroll the bottom half.

LockInfo is available for free from the BigBoss repo. Simply search for it in Cydia and install.