Wow - this is crazy. Not that I have used a modem in years, but how hard would it be to support thier own product. I actaully thought you could still buy this, but I just checked the store and they don't.
Well this one Conexant cx-fu02 (amazon) does not work
USB HSF Modem:
Product ID: 0x1300
Vendor ID: 0x0572 (Conexant Systems, Inc.)
Speed: Up to 12 Mb/sec
Manufacturer: Conexant Systems, Inc.
Location ID: 0xfa122000 / 7
Current Available (mA): 500
Current Required (mA): Unknown (Device has not been configured)
I can see it in Mountain Lion via System Profiler, but I can not access it. Does not come up as a port....