Looking for Alarm System

Hello All,

Last night, my mother-in-law passed away unexpectedly.
She grew up in a farm area with few neighbours who were more than a few miles distant.
Her residence is currently unlocked (door locks only), and we are concerned that estranged family members may attempt to remove valuables.
I need an alarm system right away, but it has to be good. The property has excellent mobile service and is equipped with ISDN and WiFi.
I read several web reviews, such as this, and wanted to hear about your experience.