This (ROS) package contains a minimal point cloud viewer (and grabber) based on the PCLVisualizer. It is based on fairly old example code, enriched by some simplistic grabbing functionality and fully supports ROS (via catkin).
In order to visualize a point cloud (online), simpy run:
rosrun pcl_online_viewer pcl_online_viewer input:=/CLOUD
where /CLOUD is the topic where the cloud to be visualized is published.