We describe the use of a single crystal of BaTiO3 as a phase-conjugator/modulator. This class of retromodulator is alignment-free, simple, and passive. By applying a time-varying electric field across a self-pumped phase conjugate mirror, simultaneous wave-front reversal and temporal modulation encoding occur within the same volume. With modest signal fields (-4120 V/cm) we observe 100% depth-of-phase modulation, with a measured bandwidth in excess of 1 MHz (scalable to >10 GHz), and with excellent conjugation fidelity. Furthermore, we observe a conjugate reflectivity of -73% using this simple geometry. Applications of such devices to remote free-space and fiber sensors and to phase-conjugator resonator configurations are discussed.