If you have changed your mobile handset, you have experienced this problem. Transferring contacts can become a messy task . The problem becomes significant when you have too many contacts, more than that you can store in your SIM memory. Other wise you can transfer your contacts to your SIM and change the handset. In such a situation an application that allows to sync your contacts online comes very handy. The idea is to develop an online service and a mobile application that works together.
The mobile application will transfer all the contacts to an online database via GPRS. After changing the handset, the same application can be used to download the contacts back to the mobile again. Regular updations will keep a back up copy of your data online also and prevent from data loss.