It seems quite believable, especially when people were watching "Gone In Sixty Seconds", (the Nicholas Cage version)
But I'm sure that since then, technology has advanced quite abit.
I have a Clifford CAT1 alarm on my Honda that was installed 7 years ago, and with every press of the button it changes the frequency it transmits (Clifford called "Anti-Grabbing Technology).
I'm pretty sure that nowadays, this sort of tech should be the norm, but of course I can be wrong.