mobile phone text service

I am proposing to create a mobile/web basedservice that will provide the user with information of the nearest (company) to their current location. This will be achieved by the usersending a sms to a number so that the user’s GPS co-ordinates can be recordedusing triangulation(or an application that can be downloaded to the phone). The number that the user sends the text message to will bepre-defined. After the user’s co-ordinates are pin pointed, the nearest (company) location to the user will be text back to the user. The (company) locations will be stored on a database behind a website; after all oftheir locations have been geo-coded I am hoping that this can be done with PHP, apache server, winamp and mysql if possible