The range would be determined by the power of the transmitter, where as the chip would be the receiver unless they're using some form of handshake between the two.They might try combining the transmitter with an induction loop to power the chip during reprogramming, which would control the range, but it still doesn't stop someone tampering with the chip while the woman is asleep.
Yes, this would likely be the partner, but this isn't a given.
It also doesn't protect the chip from outside interference which might just scramble or fry the chip.
It also limits medical investigations as this kind of implant would have to be treated the same as a pace maker (MRI scans? Sure...)
I know the BBC article on this spoke of encryption and security, but that's barely the tip of the iceburg.