<< Speeding is not privacy, its breaking the law... >>
Ummm, I believe you have no idea what the right to privacy includes, do you?
The fourth amendment guarentees a person the right to be free of unreasonable search and seizure.
"The right of the people to be secure in their person, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched and the persons or things to be seized."
Were the government to do this, it would be unconstitutional, as monitoring someone constantly without due cause just in case they MIGHT commit a crime IS an unreasonable search of their private property. There is not sufficant probable cause.
Now, since this is a private company doing this, and you sign an agreement to it before they rent you the car, it's not a violation of one's constitutional rights. But it IS an infringement on your privacy... you just have to be stupid enough to agree to it first.