I've been on post rock concert (God is an Astronaut if it helps) and during one song artist were not using something looking like tiny laptop power supply with little light (pickup side). He was still using his left hand (fretboard side) like playing normally with a pick. What was that? Is this custom effect or something?
Perhaps it was EBow. It amplifies string vibrations (using magnetic fields) providing very controllable feedback effect which allows to get very smooth and sustained sound.
Also check out this video on Youtube. Although it is old it demonstrates very wide range of possibilities of this device.