I can't comment on SMbus, but be aware of the voltage used by the vehicule (assuming it is one). In Canada, cars use 12 volts DC; PICs work on 5 V DC max. Just be aware you might need a voltage divider to lower the voltage at input, depending on the maximum voltage from the sensor.

Don't forget to compensate for any battery charging circuit as well. In Canada, alternators can go beyond 14V DC.

Robert