Communicator Recommendation?

My wife and I have for a long time been using push-to-talk communicators when backing our rig, but the darned things keep dying-batteries kaput and won't hold a charge when recharged.

A day or so ago, we were backing in our home drive. The communicators had died, so we decided to use our cell phones. What a difference! We could talk at the same time. For instance, I could interrupt her in her monologue of "come on back!" to ask a question.

So we thought-why not just use our cell phones? Of course we immediately realized it wouldn't always work out in the boonies where there is often no cell phone coverage.

So my question is if anyone knows of a good, reliable communicator that will allow both people to talk without pushing a button. I would guess that would mean separate frequencies of transmission and reception.

Any recommendations?