There's a cheap way of doing it with an old mobile phone hidden in the car and permanently hooked up to a power source. But sadly this isn't recognised by insurance companies, the subscription based one's are though.
I dont know of any non subscribtion one, the best you could hope for I think is to do what my dad did and search for one with an offer. He got one with 3 years no subscription to pay but when the 3 years where up the cost was horrendous so he didnt bother continuing it. The savings on the insurance just werent worth it.
I'm not worried about the insurance, its just if someone did take either of my cars I'd want to know where they are right away and go and get them back
