OBEX is a session protocol and can best be described as a binary HTTP protocol.
OBEX is optimized for ad-hoc wireless links and can be used to exchange all kind of objects like files, pictures, calendar entries (vCal) and business cards (vCard).
Many of the phones that do support file transfer/multimedia have support OBEX. Phones communicate in two different ways: AT Commands (like a modem) and OBEX.
When Motorola Phone Tools opens the Multimedia Center we switch the phone into an OBEX mode. The more data that resides on the phone the longer it takes to switch into and out of OBEX mode. When you close the multimedia center, we tell the phone to switch out of OBEX mode and back into AT command mode.