In general nobody in their right mind would attempt to control a printer directly these days... there are much better ways to do it.
But sending information to ports with custom devices on them such as sensors or robotics kits is something that we have thught about. We already have the Weather bug add-in and we've thought about robotics kits like Phidgets.
So Laura - can you let me know a little more about what it is you are trying to do? (If its something you don't want to talk about in public then feel free to email me directly - zman@thezbuffer.com)
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http://www.thezbuffer.com