iPowerRocket adds some settings to the standard iPhone settings app.
With „Imperial Units“, you can switch all units between metric and imperial. Under Trajectories, you can turn on/off Trajectory alerts, set the launch site altitude to use when GPS is disabled, enable/disable GPS, and set the launch speed (used to calculate rail length). Under Motors, you can set the standard setting for displaying smaller motors. You can also select which motor manufacturers you want to use.