Paul Rubenstein has suceeded in making a passive hexaphonic pickup that fits into a single coil space. Paul is a guitar player and teacher as well as an inventor (of the alumitar for example). These pickups have a separate coil for each string, allowing you to process each one indidivually. For example you could pan strings to the left or right, or have different effects on each string.
The innovative thing about these pickups is their use conventional passive electronics: most hexaphonic pickups are piezoelectric. This means electric guitar tone is preserved, albeit slightly quieter. Paul has solved problems of cross talk between strings, by somehow restricting the coils magnetic fields to cover a single string.
Paul is selling them for $110 each, this is a bargain when you consider the extra work that goes into making them. Follow the link below to find out more and listen to some sound clips of these pickups in action.
This pickup requires special wiring, most people wire the hexaphonic pickup to a 7 pin din jack, then use a 7 pin cable to connect to a breakout box with a 7 pin input and six 1/4" output jacks, one for each string and corresponding coil. Paul also sells these breakout boxes for $50, and the cable for $10 (including a 7 pin output jack at no extra charge).
Link: Ubertar passive hexaphonic pickups