The mobile version of their service allows you to access your GrandCentral account from a mobile device that has a web browser. You simply go to http://www.grandcentral.com/mobile from your mobile browser and then login to your account. From within the mobile interface you can play and manage your voicemails, view your contacts, change you settings, set temporary settings, and place calls using your GrandCentral number. While this may not be quite the "visual voicemail" functionality that will be coming in the Apple iPhone, it is much more useful than using your traditional wireless carrier voicemail system. I plan to try it out and maybe integrate GrandCentral into my life more now that I can access many of the features while on the go.
Credit: GrandCentral blog