Pablo,

Our group is working with erratic robots. As we talked the ua_erratic_player package is the current official erratic package. So we've been working with it for a while. However it has some lacks, e.g. we can't read sonar sensor values and we can't use neither the vision-ptz actuator nor the ranger-tilt-actuator.  

Unfortunately our erratics don't have a pan/tilt unit, sonar, or IR sensors that are connected directly to erratic's controller board, so couldn't really write/test any of those pieces. With that said, I will happily accept patches that expose this functionality to ROS from the player driver.

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- Regarding the vision-ptz actuator. What would be a good way to send commands? JointArray + robot_state_publisher? Maybe a look_at command topic of type Point3D??

The I would do it is the following. Since this is the lowest level driver, I would just expose each motor separately, i.e. if you have a pan and tilt motors, you should be able to control each one separately by just sending a float value that represents an angle of rotation. Things like look_at can be implemented on top of that.

- For the ranger-tilt actuator I guess is better a topic of type (Header/float).

I am not sure that the header is all that useful here. I would assume the driver will just execute the command immediately, so there's no need for Header/stamp; frame wouldn't make much sense either. I would just go for plain float, same as pan/tilt unit.