i am glad to report that the gumstix (with a breakout-gs) dialed my cellphone through gm-862 module. i just connected the STUART of gumstix to the gm-862 module to create the hardware interface. the source code is available for your review and use.
(the code is available under the terms of GNU General Public License. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.)
if you want to try this code, you need to have a a gumstix computer, a gm-862 module and a cingular wireless simcard. of course, you must connect gumstix to the gm-862 module over ST UART. btw, you also need to specify a destination number in tux-phone.h file.
an important point to note: the hardware is not connected to any speaker or microphone or keypad or display. it just dials out to prove that the gumstix can communicate with the gprs module.

Kick Ass! I think I will wait until there is working code but this is cool...

http://www.sparkfun.com/ has the gm-862 modules and a host of other geek DIY stuff