IC Design: i2c interface and manchester encoder chip

A fairly common operation in communications is the sending of an ID over a radio channel to establish a secure link. One method to do this could be to use a serial EEPROM ( 128 bits typically) with an I2C interface and a Manchester encoder. The receiver has a decoder which recovers the signal, clock and data. A chip that can do these types of functions would be a really useful device. Except that a search on the web failed to yield a product like this. One or two semiconductor companies have Manchester encode/decode devices but they are prohibitively expensive in addition to not having the needed I2C interface, serial shift register etc. etc.. A PLD could be used to do these functions except that in volume the PLDs may not be competitive. Looks like its time to do one of these chips!