I have been asked if it's possible to make an emergency key for an F-series, similar to the wallet keys from the e90/e60 generation. I suppose I can distill this question down to this: Is there a self-contained transponder (PCF7936 style) that works on CAS4+ or FEM? I've heard rumors that PCF7939VA works, but I don't know.
I'd love to just cut a generic HU100 blank and toss a transponder in it.