A surprising topic came up here at the Competitive Carriers Association’s annual trade show: eSIM, and how it might help save the business of smaller and rural wireless network operators. eSIM is a technology that promises to allow users to remotely switch from one carrier to another—it essentially replaces the physical SIM card that’s ubiquitous in today’s phones. eSIM technology was primarily designed by the GSMA for IoT applications, for example to allow automakers to ship cars anywhere in the world and then to remotely activate service for those cars without needing a technician to physically install a new SIM card for the local country.

It’s a technology that has been talked about for years, but it took a big step forward in the consumer market this year when Apple installed it in its new iPhones (that followed Apple’s earlier move to use eSIM in its iPads and then later in its cellular-capable Apple Watch).

However, in its iPhones Apple is currently promoting eSIM technology as a way for its customers to operate two phone numbers simultaneously—dubbed dual SIM—like one for personal use and one for work, or for frequent international travelers. And there are plenty of caveats around Apple’s eSIM implementation—for example, only one phone number can handle a data session; the other number is reserved only for voice calling and messaging.