Motorhome security

Could I please have your advice and suggestions for motorhome alarm systems?

I already have a professionally installed tracker system but am considering adding an alarm system covering the entry doors and lockers.  I've heard that ones that send SMS texts are very good for when the vehicle is in storage and would be pleased to hear of your experiences.

Also, I'd really apprecaite any suggestions for suitable fitters in the Beds/Bucks/Herts areas