Well 24U has a phidgets interface for filemaker:
(site seems to be down temporarily)
and here's a phidgets topic about pulse counting:
Haven't seen a compiled/working arduino connector, but it might be possible using Send Event and a command line arduino controller.
There's also a robust Java handler for Filemaker called ScriptMaster from 360works.
Any way you guy, you'll probably have some native coding required to get things to work. Phidgets is the most complete integration IMHO, but if you know Java, it might be better to go with ScriptMaster and a port connected reader.