MatchGraph! is a free game from Pasco Scientific and it is well worth playing if you have their data logging software. It uses their motion sensor and blue tooth transmitter. Connect your iPad to the bluetooth sensor and away you go. You are given different shaped distance and velocity graphs that you have to try and act out in front of the sensor. You are then marked on accuracy and given a score out of 100. The graphs range from easy to very difficult and are brilliant fun. They children loved this from KS3 to A Level who were incredibly competitive about it. It's fantastic.
I would normally get the children to draw motion graphs for their partner to act out: this is a great activity to do after they have warmed up with that as they can be assessed. With weaker groups, you can get them to discuss the shapes before they give them a go.
It's so good we even got it out for the royal visit!
is also a teacher and massive e-learning nerd.