GSM WIRELESS ALARMS

Brand new to this forum so please fogive me if this topic has been covered before........I can't find anything in a word-search.

We are contemplating fitting our motorhome with a GSM alarm similar to (but on a much smaller scale than!) our home. As a retired polis, I would regrettably far rather prefer an instant text message that my RV is being violated, than having my pride-and-joy wait for a patrol car to eventually turn up. Has anyone any experience of the Saturn wireless/wired GSM setup (see wirelessalarmsdirect.co.uk/saturn-caravan-wireless-gsm-alarm-system.html), or have any other recommendations? Muchos gracias.