Sounds very similar to common "magnetic" transducers used in place of piezos, eg http://www.sparkfun.com/datasheets/Components/CEM-1203.pdf
They show a driver ckt there, but as GM says, you can probably use an Arduino pin
directly. I've used these quite a lot on PIC I/O pins, connected via a 10-uF cap, and
reverse diode across the transducer pins. No series-R.
Since they are "coils", if you use an NPN inverter as shown in the d/s, you need to
be certain the signal never sits high constantly, or else you'll be driving a continuous
current through the device - I also use that same ckt, but with a 10uF cap driving
the NPN base.