G-tech/Pro is famous for its accelerometers or g-meters. They measure how fast you accellerate, how many G’s you’re pulling, how fast you brake and how that compares to your turns. Their SS ($199) / RR ($299) series are the top of the line, but it’s a bit unfortunate that you need to spend an extra $100,- to be able to export to your PC.
The Expandable Gauge System (EGS) is a real piece of engineering with shift lights, a rev meter, a digital display with loads of measurements all easily plugged in through your cigarette lighter and a controller. You can buy extra modules for it and expand it as much as you like. Starts at around $279
But pricing at $695 is a bit steeper