When working with our Integration kit (or -S) modules this pin is utilized by the firmware to perform a factory reset on the device. Details on the usage of this pin are documented in the Digi Connect User's Guide, http://ftp1.digi.com/support/documentation/90000565_E.pdf, as well as the Hardware reference, http://ftp1.digi.com/support/documentation/90000631_F.pdf.
When working with the Development kit (or -C) modules this pin is available to you as a general purpose I/O (GPIO). You are free to use this pin for whatever purpose you see fit.
I hope this helps.