We had pandora lite installed on our abarths about 4 years ago. Pretty reliable, tags last a long time, maybe 2 years with a cr2032 or whatever they have in them. App was always buggy - never really used it, crashed lots, and sometimes could never communicate to the car - things may have changed since then but not sure - we don't even have the app installed on our new phones.
Positives are the tags - without the tag in range the car will not start, 128bit encryption - not able to boost signal (so they say), when the app was working could monitor basic functions on car a bit like mercedes me. It auto enables and disables with factory remote / lock and unlock. Bit of a delay sometimes with it detecting the fob - but I mean you unlock car then walk up to the car and when it the detects fob it disabled the system. Anti-car jack on it is good - get pulled with the tag on you - car will shut down after a set period of time (think you can program in the app again, when and if it works). Pointless if like us you normally cannot be bothered to carry a separate lanyard and tag and the tag is on your keys in the car somewhere, but if you keep keyless go key in your pocket than maybe its ok.
Has tilt, shock sensors built in, and door / battery etc, with battery backup so even if disconnected from battery it will still work. Sensitivity of all sensors can be adjusted in the app (AGAIN IF IT WORKS!!!). Audible alert when car is bumped is good - had some kids near the cars on the drive and bump into them and it warns away, and so on. Useful if someone's going to try and bash the door lock or do something forcibly to the car to get in it that it warns them away before they do damage. If they do it twice alarm goes off.
The mis-sold the lite to us though - it has very limited number of outputs, so I didn't have all the functions I wanted wired in. So I upgraded mine to the lite-pro, with the LCD remote.
The LCD remote was quite cool but bulky, hanging it around my neck every time I went out was a bit annoying. It is supposed to alert you and enable you to control the car from about 2km away - never really had chance to experiment with it, but did provide some extra level of comfort when parked in a town / city shopping. It makes god awful tacky bleepy noises every time you lock and unlock though - very tacky and reminded me of a 90's tamagochi.
Lite pro had more outputs, and could do remote start etc, but you need to get a spare key programmed from the dealer and hidden in the car with the system - dodgy as to me, why on earth would I want to leave a fully coded factory key in the car somewhere!!!! So kind of pointless if you ask me.
The lite was about £500-600 back then, lite pro about £1000+, and the 'elite' system with tracker etc was £2000. Add the cost of a spare key from the dealer and additional fees for extras and fitting.
I have an aftermarket tracker on the merc (not the mercedes me one - waste of £29 a month - don't trust it, plus notifies on the screen, plus app is buggy as hell, so gives me no confidence it is reliable, mis-reports car ignition status often, so even disabled the remote lock unlock features etc, not impressed!).
Had a ghost - annoying to be honest, I want to get in my car press one button and go, not piss around pressing buttons on the car like I am trying to enter a cheat code on a 90's console controller every time I want to start the ignition, but believe a fob is also available (haven't tried the fob, but makes sense if more convenient). Downside to the ghost? Well no one knows the car has one, so as with cars like the abarth, by the time a thief has bent the hell out of your door frame and hammered the locks, connected the OBD start tool, your car is already badly damaged - I think the point of having a good imobiliser system is to not only prevent it being taken, but to also try and stop damage, so ghost does not get my vote.
Honestly I think the best value and most functional option is the pandora lite. I really should load up the app soon and see if it works properly now - it crashed on open on my old phone after an update and neither the UK headquarters or anyone in their support network knew what to do, plsu back then confusingly they had multiple apps on the appstore, with some being buggy and some being more compatible than others with certain models - not the best.
Pandora also comes with an over-ride card, but good luck putting the code in with just one button in the OBDport area - had to try it before to reset the system and it was a nightmare! Again though, thankfully the one fitted to the wifes car we just fitted and forgot about and its 99% reliable once we configured it to how we want and we just left it with occasional battery changes to the tags.
Hope some of this is useful to you.