The challenges require you to perform specific actions with the specified weapon to unlock new upgrades and special attacks. (darkstation.com)
With this chosen path, the actual gamer controls more of what they want to accomplish instead of performing specific actions to move the plot along. (thatvideogameblog.com)
From the developer that brought you SMSbyNow On Location is not as drastic as that but it is a headless application that performs specific actions when entering or leaving a location. (crackberry.com)