Yes, a capacitor arranged so that you have a charge pump circuit. Only a signal that changes rapidly will build up a charge good enough to switch a comparator. Inductive decoupling would be like a pulse transformer, again only a signal that changes state rapidly can cross the isolated barrier via magnetic flux variance in the transformer. You have to implement this through a current limiting resistor so that if the port state is active high, you will not damage the switching device, like a mosfet, or bipolar transistor.
The example in the download page is apparently good, but I have not used that one.
Whacko