Allmost two years ago, I began my experiments with RFID, writing support for 3M 810 RFID Reader. Then I tried to make web interface for RFID it in Koha.
This woked, but having separate Comet server was too much complexity for me, so I decided to implement JSONP directly in RFID driver code. Hack, I allready had HTTP server, and local JavaScript interface, so why not?
Move to JSONP allowed me to use original Koha web interface, and just overlay RFID information and form submission code as simple jQuery snippet.
But, two years of development and trying out different approaches produced not-quite-production-quality code. So, I began rewrite called Biblio::RFID. It splits RFID reader support from HTTP and JSONP servers and couples this with documentation and tests. I have production use for it this summer, involving programming of RFID cards as they are printed out, so expect it to change during next few weeks. After that I will push it to CPAN, but I would love to get feedback and comments before that.
Update: It's also availale at CPAN.