Is a battery cutoff switch possible?

[K clio]

I've often thought that a simple anti-theft device for your average car would be a battery cutoff switch hidden away somewhere. Is this easily possible to install? As the battery leads are quite thick, maybe it would burn out too quick or there are other reasons why not.

 

[JamesBryan]

It's possible, but not really needed.

Who's stealing Clio's these days.

Plus the central locking wouldn't work once the power is cut off. Not all of them have key barrel locks in the doors.