When I put new airtime on my tracfone they ask for the ESN and then they give me a code to put into the phone. So I was thinking to make a generator you need to figure out how they get the code using the ESN and what the date has to do with it and the # of minutes. So theirs 3 veriables that make up a tracfone code. It will be hard to crack but someone should be able to do it.