Cheapest Pay-as-you go phone plan

My wife and I are about to retire and hit the road full-time in our AS 30' Flying Cloud. She has an iPhone 5 with Verizon and I have a cell phone through my job which I will be giving up. I'd like to buy a cheap cell phone as a backup and for calling my wife on the rare occasions when we're separated. The cheapest deal I've found so far is from PagePlus which is a pre-paid plan of $10 for 100 minutes and lasts 120 days. If I don't go over 100 minutes in 120 days (which I probably never will), this comes out to $2.50/month plus a $0.50/month service charge. Has anyone found a cheaper deal for someone who rarely, if ever, uses their phone? Also, if you have service with PagePlus, I'd like to know what you think about their service. It's my understanding they're a reseller of Verizon. Thanks.