I have looked into this opportunity two years ago. here are my research: 1) USA carriers like Verizon offers a service charging $5 a month to backup contact 2) Carriers in China offers for free. But you have to input them first. But you can query your contact book using SMS. I assume their online contact book sync with your Outlook 3) In 3G, there is a mobile contact book XML standard, using which you can sync with any online contact book supporting that standard on 3G network. There are plenty of startups doing that already since it's so simple to implement.