As for just plugging an Arduino into a phone, that won't work because they are both perifierals and neither is a host. Their are host shields for the Arduino, but things can get complicated going that route.
Hi , I first wanted to make a Windows Phone application for blind people in order to help prevent them from getting hit by surrounding objects as my graduation project!!, I have an Arduino Board, an UltraSonic MaxBotix LV-1 Sensor, and a USB.Now after a 1 year work I found out that it is impossible to exchange data between the Windows Phone or emulator and the Arduino Board via USB . Is there any Ideas I can use or change my project making what I have ( the sensor, arduino , usb) useful? I need new Ideas!! Pleaaase