Well in my boredom on the way to work I thought I would give my "Tightwad Performance logger" a run. Basically, on the Nokia platform a program called Racechrono (It's free) uses the internal GPS to track speed and it allows you to record performance data.
However, one important feature is it allows you to use an external GPS. On ebay you can buy a 5Hz GPS receiver for £25, which in theory should give you accuracies of around 0.2s as opposed to 1s of normal GPS systems. It's not quite 0.01s of a racelogic box, but then it only costs £25

So on a dual carriageway into work I recorded the following data in the Peugeot Diesel power machine
The program reported the runs as (I think it interpolates the data to some degree):
Run 1 12.06s
Run 2 12.19s
Run 3 12.37s
I've also plotted altitude on there as one run was a slip road but I got off to a poor start but it still returned a similar run to number 2 I was hoping to set a record! Run 1 was 2nd>3rd>4th 2 and 3 were 3rd>4th
Just thought this may interest some people as I know things like the GTech were popular (The ones that use accelerometers similar to the Dynolicous program on the Iphone) And I think this is a lot more accurate than accelerometer based systems.
Ben