Hmm. We have the couples plan too with Rogers, but it doesn't work when we are away from home--still get LD charges as we are "calling" NS even if we are calling a few hundred metres away. I wonder if our plans are different or if you're just doing something we're not. We asked before we left and were told it would be $40 for the month, but each phone had to have it. (As we mostly wanted to be able to call each other if separated.) Hoping our deal with them will expire by the next time we go--I should check! I didn't actually see our bill last month, a mailing error, but it was $80 more than usual (for VERY FEW calls, maybe--10 short where-are-you things), so we might as well have gotten those two $40 plans for the month.
More research for me next time, it's the perfect use for cell phones.
I have heard from others that walkie-talkies and radios tend not to work well as lots of others have sets competing on a relatively narrow range of frequencies.