I'm a fellow Sanibel resident (French Oak Avenue) and we use Frontpoint Security. We have been very happy with their system and especially with the customer service. You might check them out.
Total Security, Big Savings | FrontPoint Security
Also, would it be worth our time for someone from the Sanibel Heights Neighborhood Association to contact Frontpoint and other security companies about a group discount for anyone in the Association who might want to have the service? There is usually a discount available when groups purchase in volume. Just a thought. It would be easy to try to arrange a discount and then survey the Association members via email to see how many might be interested. We could turn Sanibel into the most protected neighborhood in The Villages!