Ok with some help from the main site. I went and brought the iBlue bluetooth GPS receiver.
Use it on the weekend. It is good. The accuracy is better than I thought. It is within .10 of my AIMS timer which is as good as anything on earth.

This shows the Phillip Island circuit.

This show the lap times... it is quite comprehensive. And you can analyse each lap showing all the speed around each corner too.

You can set the trap as you go or afterwards. You can set a trap retrospectively to show how much difference in each corner so you can improve~~~!!!!!!!!!!
Top toy.