A visualiser or Flexi Cam is like a webcam.
There is a small digital camera in the head of a flexible arm.

The visualiser is plugged into a computer via a USB cable. There is no need for a power cable. The camera takes the required power from the laptop.

As you can see in this photograph the flexi cam image appears as a live image on the computer. It can then be shown to a class on an interactive whiteboard via a projector. You can freeze the image and write on it (on the IWB).
A photo can then be saved by pressing a button on the computer.
A flexi cam can also show live video. This is rather like the cameras that you see when you enter certain shops. Again it can be used via a projector so that a whole class can follow a demonstration or activity.
Visualisers vary enormously in price. I have been using a Flexi Cam (by Ken-a-vision) for about 3 years in my previous school and found it to be a valuable and 'flexible' tool in the classroom. At Robert Hitcham's we have just purchased a visualiser / flexi cam for every classroom from Aver Vision. We have paid about £230 for each visualiser. They have a 3mega pixel camera and video capture. It is worth shopping around for a good price.

They can be used to show documents, children's written work, passages from a book, paintings / drawings, 3D work or objects brought into the classroom. It can really save on photocopying. One of the best learning uses is when using the live video function. It is great for demonstrating a skill to the whole class. Children who can do something really enjoy showing others via the flexi cam. It is much better than asking the whole class to 'gather round'.

In order to make the most of a flexi cam then it is worth getting into the habit of setting it up every morning. There are unplenned moments when it will become useful in a lesson - so it is best to have it ready. Don't forget that it is basically a camera so it canbe used to record the children's work in a whole range of subjects. You can also zoom in for a close look at work or objects. Some visualisers can be connected to a microscope.
It is a fantastic aid to learning and I would recommend one to teachers of all age groups or subjects.