In order to use a cell phone to control arduino you need to have installed a bluetooth uart module to your arduino. The other part is the software installed in your phone. The software is a java j2me application which uses bluetooth to connect to the uart bluetooth module. I am using Nokia 5000 but I have tested the application also with Nokia 2600 classic. The devices which support Java JSR-082 (Bluetooth api) and my app are located here The application is loaded to the phone using a bluetooth connection. The application is Open Source and can be modified and compiled with NETBEAMS IDE in order to suit your needs. For details and more pictures
After the application starts it does the following: - connects to the bluetooth serial module - loads the user interface
In my case every checkbox has an assigned message for example if the checkbox is checked it sends the string "on" to the bluetooth module after pressing enter. If the checkbox is unchecked it sends "Off" to the bluetooth module. Of cource there are various items which can be used as input for example textbox, button, scroller, combobox, also a specific action can be assigned for the phone keypad like left right up down for buttons 4,6,2,8. With the nokia 5000 and a Class 1 Bluetooth module like BTM-222 the Direct LOS range is about 45 meters.