Alarm System on PIP

Only comes with a passive anti-theft type device (i.e., the key has a chip, making it difficult to steal the car). I personally prefer Viper & Compustar systems (have a 2-way Compustar in my other car).

Both those manufacturers also offer a module which gives you control of the car over the internet. What system you go with, make sure you get it installed via an authorized dealer/installer (so avoid the eBay specials).

That said, as far as I know, it barely makes any difference on my insurance last time I checked.

 

Although not plug in related, My 02 prius with the type of factory alarm that sets off the horn due to an open door or if glass is broken saves me a whopping $12 a YEAR through State Farm ins. However, your insurance and the area you are in may or may not save you more money..