A good faraday pouch. As well as a metal tin hidden somewhere.
Also a friend of mine as a ghost alarm and it's brilliant, that's the best security option. As well as having the old fashioned steering lock etc. Also you could get anti break film for the windows. Also when parking try and keep it boxed in.
My advice would also boost house security too.
However I would say if they want it they'll take it. At knife point in some cases. Truthfully in my case I actually leave keys near the front door as id rather them take the car rather attack me or my family.
Cars can easily be replaced. Humans or pets can't.