Here's a link to a clip of the NASCAR technology (TV, not cars obviously). Here's how they do the NASCAR stuff.
Here's how they do the yellow first down lines. I was surprised that the calculations take so long that they have to insert a delay in the audio to keep things synced up.
A related gadget is Skycam from CF InFlight. Here's what it looks like:
And here's how it works.
Interestingly, in a recent Formula 1 broadcast, they had a tachometer overlaid on the screen. The RPMs were over 19,000 which is pretty high even for an F1 engine. The commentators pointed out that the RPMs were calculated from the frequency of the exhaust sound.