I had to make a little Mac OS X application that check if the processor has a 64Bits instruction set or not.
I made that for WebStart, as it only run on 64Bits machines, so users can test their own processor before downloading and buying the software.
It's not a great deal, since there are
__i386__ macros, but in case you need such an app, it's available on GitHub, released under the Boost license.
Feel free to use it:
I also made the icon myself, which is available in 2000px. Also feel free to use it without copyright limitations if you need it!