If you have a handheld I'd suggest avoiding a custom solution. Use one of a few hacks out there for the Palm platform to collect IR. One example is USB-2-IR written by Matthias Ringwald. It passes IR through the cradle and thus through the USB to your PC.

Someone else has a utility to 'capture' all received IR and 'repeat' it back out... I'm having problems finding it at the moment though.

Wouldn't these work? Assuming you have a handheld.