I already had a cat S5 tracker, which allows ME to track the car on the app. As I understand it, the Lexus one is a cat S7, which only allows the tracker co to track the car after it’s gone missing. A geofence device can also be provided by Lexus which I’m guessing would ping your phone when the car leaves a predetermined area.
Lexus refunded me half the cost of my tracker a couple of months ago, rather than fit theirs alongside my existing better tracker. I also had an immobiliser upgrade fitted when my tracker was fitted - that imho is essential.
An Immobiliser is the only sensible option - having a tracker doesn’t stop it being nicked, and relying on a third party to track the car using Lexus’s tracker didn’t appeal.
The key to all of this is some sort of visible deterrent. Trackers and immobilisers still don’t stop attempted theft.