Celica Forums General Discussion General Aftermarket electronics to measure my speed

I was curious what products are on the market to measure my true vehichle speed. I know of the APEXi RSM system. Are there any others? My speedo is all screwed up, and since I've always wanted one of the portable performance meters, I was looking for something that measures speed too.

Here's another question: If I got the APEXi Power FC as a replacement for my factory ECU, does that allow for tire size correction? Will it allow a user to input that the current tires on the car are not the same size as the factory tires?

G-Tech pro?

GPS??? for instance a Garmin PDA...

Doesn't do it. Only measures performace features. That was the one I really wanted.