This is probably the worst solution for the problem. However; you could bridge a PHP CLI program with a websocket html page which runs in kiosk mode.
For reading the comport:
http://blog.950buy.com/article/php-use-rs232-serial-communication-to-send-file/
For more information about websocket and a client/server websocket implementation:
http://www.sanwebe.com/2013/05/chat-using-websocket-php-socket
- PHP Forloop reading the comport.
- If information is found; push to websocket
- Webpage listens to websocket and get the information in json
- Webpage decodes the json and display's information
Again; i feel a bit uncomfortable that you're trying to sell this to someone probably without telling that you are going "to transfer a valuable load using fireworks". This methaphore doesn't make sense, like your choice of language.