Is Lo-Jack a sensible purchase?
Offering my opinion, it is going to get stolen and trashed, or taken to a chop shop and trashed, why would I want it back.
The car I bought came with it free of charge. It does result in a dicsount on my insurance, so it might be worth it for you. Ask your insurance agent how much of a discount it would be worth and do a break even analysis to help you decide if it is worth buying. If you are in a position to haggle, see if you can get a price that makes it pay for itself.
It could result in a 5% to 10% insurance premium reduction as an Anti-Theft feature. If you’re going to keep your car long enough that the insurance reduction pays for the feature, take it! (say your premium is $1000/year. If having lo-jack knocks that down to $900/year, and lo-jack costs $300, will you be keeping your car more than 3 years?)