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that would be my suggestion is a cell phone with the walkie talkie feature. most CB's only have about a 5-7 mile range without an amplifier (linear) hooked up to them and those can be a little pricy. another option would be 2-way radio system.
CB's aren't going to give you much range at all. FRS will give you a little more, but not 12 miles probably. I have the 36 mile Midland radios and I can only get about 5 miles clearly.
I work for a security system company and we use the Sprint PTT phones (used to be Nextels) They work awesome for what you want to do, as long as you can get service out there.