In the event that you want to have speeddial-like functionality from the Lock Screen, you can use a new jailbreak tweak called PassDial Pro
by iOS developer Sassoty to assign different contacts' phone numbers to different "passcodes" on your Lock Screen.
We put the word "passcodes" in quotes, because they're not really passcodes as much as they're just little shortcuts that could be disguised as passcodes. Basically, even if you have a passcode (say, for example, your passcode is 0987), you can assign a contact's phone number to 0000 and if you enter 0000 on the Lock Screen's passcode screen, you won't get granted access to your iOS device, but instead, your iPhone will begin a phone call to the contact that you have assigned to the code 0000.
The tweak adds a preferences pane to the Settings application where you can enable or disable the tweak on demand:
There are also two cells in this preferences pane (one labeled Phone and one labeled FaceTime). Any of the contacts' phone numbers that you put under the Phone section will call as phone calls from the Lock Screen when you invoke one of them via the passcode-based shortcuts, while any of the contacts' phone numbers that you put under the FaceTime section will call as FaceTime calls from the Lock Screen when you invoke one of them via the passcode-based shortcuts.
When you're ready to assign a passcode-based shortcut to a contact's phone number, you can tap on either of the cells. In this case, we want to add a shortcut to calling (123) 456-7890 with the passcode 0000:
To do this, we would tap on the "Add Entry" button, and in the prompt that comes up, we will enter that person's phone number, and then enter the passcode-based shortcut that we want to use to call that person, and then tap on the "Save" button to save our changes. From this list where the "Add Entry" button was, there's also a button labeled, "Remove Last Entry" that lets you delete the entries you put in.
PassDial Pro lets you add add up to 10 Phone and 10 FaceTime password-based shortcuts simultaneously, so you can have a big speed dial database without ever having to unlock your device. If you're unsure about buying PassDial Pro at this point in time, you can try out the free PassDial tweak, which does the same thing, but limits you to only a maximum of five passcode-based shortcuts.
Notably, if you have a Siri-enabled device, this tweak might seem far-fetched as you can easily tell Siri to call someone for you, but if you're using an iPhone 4, this tweak might be a somewhat feasible option. One downside of the tweak is that you have to manually enter contacts' phone numbers instead of just picking contact information from a user-friendly picker of some sort. Additionally, you'll have to remember the passcode-based shortcuts that you assign to contacts.
If you want to give PassDial Pro a try, it's available in Cydia's BigBoss repository for $2.00. It's compatible with both iOS 6 and iOS 7.
Coming soon, the developer will let you add an unlimited amount of passcode-based shortcuts to contacts, and the ability to launch specific commands or applications via passcodes.
iPhone 5 running iOS 7.0.4