The RCX has been set up real simply with three touch sensors, one for left, one forward and one right. The programming is made pretty easy using NQC:

task main()
{
  /* Set all three Sensor types to Touch sensors */
  SetSensorType(SENSOR_1, SENSOR_TYPE_TOUCH);
  SetSensorType(SENSOR_2, SENSOR_TYPE_TOUCH);
  SetSensorType(SENSOR_3, SENSOR_TYPE_TOUCH);

  /* Set infrared power to High, so we can cover longer distance. */
  SetTxPower(TX_POWER_HI);

  while(true) // Loop forever
  {
    if (SensorValue(0)==1) //button 1 pressed
    {
      SendRCMessage(RC_CHANNEL_1, RC_CMD_REV, RC_CMD_FWD);
    }
    if (SensorValue(1)==1) //button2 pressed
    {
      SendRCMessage(RC_CHANNEL_1, RC_CMD_FWD, RC_CMD_FWD);
    }
    if (SensorValue(2)==1) //button3 pressed
    {
      SendRCMessage(RC_CHANNEL_1, RC_CMD_FWD, RC_CMD_REV);
    }
    Wait(5);
  }
}

This of course assumes your Spybotics brick has been configured to RC channel 1. Download the program: rcx2spy_remote.nqc