Human memory is important yet often not easy to be handled in daily life. Many challenges are raised, such as how to enhance memory recall and reminiscence, how to facilitate memory sharing in terms of people's social nature. This paper proposes MemPhone, a new system that addresses various human memory needs by using the mobile tagging (e.g., RFID, barcodes) technique. By linking human memory or experience with associated physical objects, MemPhone can i) augment memory externalization and recall, and ii) build object-based social networks (OBSNs) to enhance memory sharing. By embedding physical contexts into SNs, the OBSN can strengthen friendships by enabling serendipity discovering and nurture new connections among people with shared memories. Early studies indicate that our system can facilitate memory recall and shared memory discovery.