Basic aftermarket alarms are dirt cheap and most times free installation depending where you go
Personal opinion dont bother with alarms , i work in a body shop no matter how much "safety sense" and cameras and automatic collision breaking etc...hasn't changed the flow of cars coming in if not we have more. Now no matter what alarm whether factory or aftermarket cheap or pricey, junk car or expensive, cars still get broken into and we get whole strings of theft jobs
Now alarms are only a DETERER , they only increase the chance of a thief being deterred, if they wanna break into your car alarm or not they going to do it!
My tacoma only has factory engines kill and a flashing light on the dash. That flashing light give you the same odds of deterring theif then a whole alarm system