My first question would be ... have you got an alarm fitted already?! If not your insurance company may be iffy about a theft related claim! If you havent got one then your car must be an import.
I expect what Im about to write has all been written before in past posts but here we go...
The standard alarm/immobiliser as fitted to the 172 (and probably other Clios) is actually a Cobra product. It may say Renault on it but is just a rebranded Cobra deal. 172s come as standard from the factory without an alarm and one is fitted on arrival at the docks in the UK by Renault UK to bring the security upto Thatcham Cat 1 spec.
If you fit the Cobra alarm you have the potential of having your alarm rigged to your existing key plipper rather than having a separate plipper.
Double check what is Thatcham 1 approved. This is important as most insurance companies will not insure a car like the 172 unless you have decent security. Practically any system from a well known car security company will be approved but it doesnt harm to cast your eye over
http://www.thatcham.org/resources/pdfs/compliance.pdfhttp://www.thatcham.org/resources/pdfs/compliance.pdf
If you do get an alarm fitted make sure its from a VSIB accredited installer. If you dont you may find your insurer has itchy feet if you ever unfortunately have to make a claim! You may pay a bit more over Dodgy Dave Security Consultants but itll probably be worth it and they wont trash your car!
Personally I dont reckon a shock sensor is probably worth it. Cat 1 gives you all the stuff you need with perimetric and volumetric detection.
Hope this helps!
