Im not quite sure how exactly my friend makes these devices... regarding fakie 02's
I am the mechanic and sheet metal guy, hes my programmer and software guy who owns a commercial voice over IP company... Ive known him since grade 3 and he is the computer wizard in my books. Taught me how to build my own computers and what not.
From what I gather though, yes its is some resistors. The fake 02 my friend gave/built me has a PIC controller though, it takes regular 12V power and it goes inline with the post cat 02 sensor, you then can just dangle the post cat sensor under the frame somewhere in the open air, as long as its plugged in it wont throw codes... does not have to be installed in the exhaust. Mind you, I am somewhat taking a guess that it would work for a OBD-II Ram, as my Ram has only the single 02 so I do not need the fake one. The fakie 02 my friend built me was for my 98 Bonneville SSEi, and it works fine on that OBD-II car with deleted cat and dual 02's.
He has done some crazy shit for me in the past, custom chip for my 91 Buick Lesabre Limited for higher octane and to support my ported heads, LIM, CAI, and Harland Sharp 1.9 roller rockers, he made me a serial line driver for the ALDL port to interface with some ALDL software this Australian company makes out of old serial mouse parts so I get a laptop screen full of swankie stats in real time while I drive... He even put slap shift tranny contoller in his dodge intrepid from a eagle talon TSi. He does crazy shit and takes him maybe 2-3 days tops. I could see if he would like to mass produce his PIC controlled fake 02 sensors.