I"ve got an Escort 8500I - is has GPS and remembers what it hears. If it sees the same signal at the same spot three times in a row, it stores it as a false signal and won't trigger on it anymore.

But with "instant on" mode in modern radar, Nick got nabbed on the last Dragon trip with me (and my detector) riding along with him. The RD helps, but it is not a cure-all.
And it makes me too brave - Nick is thinking of buying it and if he doesn't, I'm taking it to the Lawrenceville Hamfest November 1st and putting $300 on it.