The doc shown below does map GPIOs to individual pinouts on the back of the verdex pro.  Breaking out my volt meter I was able to confirm that indeed:
 
echo "GPIO out set" > /proc/gpio/GPIO??
will show 3.3 volts.
 
echo "GPIO out clear" > /proc/gpio/GPIO??
will drop the voltage back to 0
Thus I can build a simple circuit that opens and closes based on the voltage change. 
Thanks for the help guys!

From: Dave Hylands <dhylands@gmail.com>
To: General mailing list for gumstix users. <gumstix-users@lists.sourceforge.net>
Sent: Wednesday, April 29, 2009 2:16:04 PM
Subject: Re: [Gumstix-users] GPIO

On Wed, Apr 29, 2009 at 10:10 AM, Rizal Nor <joey.aka.rizal@gmail.com> wrote:
> Hi Donald,
> It was confusing for me too. And, im still a bit confuse.
> In the schematics, I couldn't find which pin connects to which GPIO.
> As I understand it, the UART lines are UARTs, they are connected to their
> own GPIO pins and can be activated or turned off, if you know which GPIO are
> managing them.

The mapping of GPIO pin number to pin function can be found in a
variety of places.

For example, this page shows the mapping of the pins on the 60 pin connector:
<http://docwiki.gumstix.com/index.php/Verdex_60pin_connector_chart>

All of the above information ultimately comes from the PXA270
Technical Reference Manual:
<http://pubs.gumstix.com/documents/PXA%20Documentation/PXA270/PXA270%20Processor%20Developer%27s%20Manual%20%5b280000-002%5d.pdf>

Chapter 24 covers GPIOs, and page 997 has the mapping of which pin
maps to which GPIO number.

--
Dave Hylands
Shuswap, BC, Canada
http://www.DaveHylands.com/

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