Add a shortcut to your springboard to call the person of your choice.

You can select any number from your adressbook or even enter another number.
Once registered, all you need to do is tap the icon to call that person.
You can always change the number of the recipient in "Settings" to enable or disable the option "Confirm Call" and to display an alert asking you to confirm the call.

So you can put one of your important contacts on your springboard to call him in one movement.