There are several other makers of voting systems. The Promethean system is very easy to use and I have found that children like the handsets.
These are radio linked with a receiver plugged into the classroom computer (linked with whiteboard).
The handsets allow children to respond to questions written on an interactive whiteboard. These questions can be prepared in advance on a flipchart or produced on an ad hoc basis during a lesson. The teacher can simply write a question with the activ board pen and click on the voting icon. The children will then vote with their handset. Their responses are recorded and can be displayed as a bar graph or pie chart. All the questions during a lesson are recorded so that the teacher can see each child's voting pattern.
I have found voting to be a great way of engaging children at the start of a lesson. I often use hand written questions during an activity to find out if the children understand a particular concept. The beauty of voting is that it enables every child to respond to a question instead of children needing to put their hands up. The teacher gets 30 responses instead of one.
The instant feedback combined with the children's enthusiuasm (for activ voting) adds a very powerful element to the learning process.
I have made voting a regular part of plenaries in maths and science lessons. This obviously gives me important feedback on the class and individuals learning from a lesson. In literacy lessons I have used voting for some spelling activities.
One of my favourite uses for voting is in conjunction with interactive programs. The voting system enables the whole class to interactive with the program instead of just a few individuals.