gTalk PBX service offers a smart-phone app (application to do a number of useful functions at no additional cost). The app extends reach of your gTalk PBX to anywhere through the Internet. So irrespective of geographic location gTalk app allows your employees to remain within company's PBX network, as if he/she were in office.
Your company can avoid expensive roaming charges it currently incurs for having your traveling employees remain in communications with your office. The app as usual offers one touch calling features for intra company calls.