They are more for fun, and not to be taken too seriously, since they can be highly inaccurate.
On the other hand, since they are inaccurate, and taking into granted that it's a constant state of inaccuracy, you could probably use it to work on certain things such as your 0-60, quarter mile, 1-2 shift, and other shit like that.
You could also use it to give a rough estimate of how much a bolt on mod could have helped you.