cf. http://vimeo.com/24608862 !

example.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE properties SYSTEM "cpf.dtd">
<properties>
<simple name="Import" type="string"><value>rtt_ros_integration_example</value></simple>

<struct name="ROSConTwistOut" type="ConnPolicy">
  <simple name="type" type="short"><value>0</value></simple><!-- type of connection: 0 means Data -->
  <simple name="size" type="short"><value>1</value></simple><!-- buffer size -->
  <simple name="transport" type="short"><value>3</value></simple><!--3 means ROS-->
  <simple name="name_id" type="string"><value>/ATRV/Motion_Controller</value></simple><!-- topic name -->
</struct>
<struct name="ROSConLaserIn" type="ConnPolicy">
  <simple name="type" type="short"><value>0</value></simple><!-- type of connection: 0 means Data -->
  <simple name="size" type="short"><value>1</value></simple><!-- buffer size -->
  <simple name="transport" type="short"><value>3</value></simple><!--3 means ROS-->
  <simple name="name_id" type="string"><value>/ATRV/Sick</value></simple><!-- topic name -->
</struct>

<struct name="HelloRobot" type="HelloRobotLaser">
  <struct name="Activity" type="PeriodicActivity">
    <simple name="Period" type="double"><value>1</value></simple>
    <simple name="Priority" type="short"><value>0</value></simple>
    <simple name="Scheduler" type="string"><value>ORO_SCHED_RT</value></simple>
  </struct>
  <simple name="AutoConf" type="boolean"><value>1</value></simple>
  <simple name="AutoStart" type="boolean"><value>1</value></simple>
  <struct name="Ports" type="PropertyBag">
    <simple name="twist_out" type="string"><value> ROSConTwistOut </value></simple>
    <simple name="laser_in" type="string"><value> ROSConLaserIn </value></simple>
  </struct>
</struct>

</properties>

HelloRobotLaser.cpp

#include <rtt/TaskContext.hpp>
#include <rtt/Port.hpp>
#include <geometry_msgs/Twist.h>
#include <ocl/Component.hpp>
#include <sensor_msgs/LaserScan.h>
#include <numeric>

using namespace std;
using namespace RTT;

class HelloRobotLaser : public RTT::TaskContext {
private:  
  InputPort<sensor_msgs::LaserScan> inport;
  OutputPort<geometry_msgs::Twist> outport;

public:
  HelloRobotLaser(const std::string& name):
    TaskContext(name),
    inport("laser_in"),
    outport("twist_out")
  {
    ports()->addPort(inport);
    ports()->addPort(outport);
  }
  ~HelloRobotLaser() {}
private:
  void updateHook() {
    sensor_msgs::LaserScan msg;
    if (NewData == inport.read(msg)) {
      geometry_msgs::Twist cmd;

      bool halt = false;
      for (int i = 75; i <= 105; i++) {
        if (msg.ranges[i] < 2.0) {
          halt = true;
          break;
        }
      }
      if (halt) {
        double midA, midB;
        cmd.linear.x = 0;
        // we go to the highest-range side scanned
        midA = std::accumulate(msg.ranges.begin(), msg.ranges.end()-90, 0);
        midB = std::accumulate(msg.ranges.begin()+90, msg.ranges.end(), 0);
        log(Info)<<"A:"<<midA<<", B:"<<midB<<endlog();
        if (midA > midB) {
          cmd.angular.z = -1;
        } else {
          cmd.angular.z = 1;
        }
      } else {
        cmd.linear.x = 1;
      }
      outport.write(cmd);
    }
  }
};

ORO_CREATE_COMPONENT(HelloRobotLaser)

manifest.xml

<package>
  <description brief="rtt_ros_integration_example">

    <include virtual="doc.html"/>

  </description>
  <author>Ruben Smits, ruben.smits@mech.kuleuven.be</author>
  <license>BSD</license>
  <review status="unreviewed" notes=""/>
  <url>http://ros.org/wiki/rtt_ros_integration_example</url>
  <depend package="rtt_ros_integration"/>
  <depend package="rtt_ros_integration_std_msgs"/>
  <depend package="rtt_ros_integration_geometry_msgs"/>
  <depend package="rtt_ros_integration_sensor_msgs"/>
  <depend package="rtt_ros_param"/>
  <depend package="rtt"/>

</package>

wifibot.py

from morse.builder.morsebuilder import *

# Append ATRV robot to the scene
atrv = Robot('atrv')

# Append an actuator
motion = Controller('morse_vw_control')
motion.translate(z=0.3)
atrv.append(motion)

# Append a sick laser
sick = Sensor('morse_sick')
sick.translate(x=0.18,z=0.94)
atrv.append(sick)
sick.properties(resolution = 1)

# Insert the middleware object
ros = Middleware('ros_empty')

# Configure the middlewares
ros.configure(motion)
ros.configure(sick)