What about the high quality walkie-talkies that are now available? Most of the high quality ones have a long range (some have a range of several miles), and there is no monthly fee involved at all.

Here is a fairly recent article from USA today about the new higher-tech walkie talkies (that are usually called 2-way radios now)-
http://www.usatoday.com/tech/columni...7-kantor_x.htm

My brother (a college student) bought a set of these long range 2-way radios - he kept one for himself and gave the other to his girlfriend so they could talk to each other at any time... these 2-ways have such a long range that they can talk to each other no matter where they are on their college campus (which is quite large). And the units themselves are quite small (although there are other units available that are larger if you prefer a larger unit).

I don't know if these newer walkie-talkies (long range 2-way radios) would work for your situation, but it was the first thing that popped into my head when I saw your post.

Take care,
Liz