Well, When I was in Pakistan 4 months back , I was working in the field of Remote Monitoring.
Let me tell you guys one interesting fact that almost every tracking company is using the same devices ( I will refrain from mentioning the Manufacturer) .
So , every one is almost on same platform as far as technology is concerned ( Even CTRACK) ,the difference lies in the Customer Support and the Recovery Department.
Now , The AntiJammer technology which is mentioned here in some of the posts, What is does is it stops the vehicle when it senses that GSM Signal is being Jammed. But that is also not 100% sucessful and it is in early development phases ( Right Now even the circuits are hand made in Pakistan) .