Pagers were once a great way to get a message to someone out in public; they just had to be cool enough to have one. These days, they’re mostly the preserve of doctors and a few other niche operators.

The small plastic box that beeped and flashed numbers was a lifeline to Laurie Dove in 1993. Pregnant with her first baby in a house beyond any town in rural Kansas, Dove used the little black device ...