Sony has been big on smartphone integration for car audio lately, having already launched its MirrorLink receivers earlier in the year for the more well-heeled drivers among us. The company is bringing that mobile tie-in down to Earth through a new quartet of in-car CD receivers. The MEX-GS600BT, MEX-BT4100P, MEX-BT3100P and CDX-GS500R all bring in App Remote, which lets the faceplate buttons steer local music or Pandora streaming radio coming from Android, BlackBerry, i
