Use the speed-dial feature, available either from the ObiTALK page or directly on the device webpage (under user setting).
For me, I use speed dial #8 as a short cut to call my home OBi, e.g. **9200123456 as entry into speed dial 8.
To use the speed dial, just press 8 from your phone (there is a 2 second time out), it will dial out that number, or you can press 8#, it will immediately dial out that number.
