Will work until thieves learn how to disable it. Maybe a device slipped into the handle bar, or onthe BB powered by the crank.
http://1sun4all.com/bikes/bikespike-new-device-lets-you-track-your-bike-and-detects-thefts-crashes/
Yes, it does not look very secure and I certainly don't want to give up my extra bottle cage. A bit pricy at $199. I never let my bike out of my sight....