BARCELONA—If you plan to use lots of data abroad, you'll need a global roaming hotspot from companies like Skyroam or RoamingMan. But if all you want is to keep your phone connected, there's no need to shell out for an expensive roaming plan from your carrier.

Telna has offered SIM stickers for some time now, letting you call, text, and get data abroad. Now, in partnership with Xiaomi, Telna is adding virtual SIMs to 100 million users of various Xiaomi handsets.

"It's a SIM card technology we developed," said Telna CEO Gregory Gundelfinger. "It's a hardware solution and a software solution. There's no SIM card inside. These are all devices that incorporate a SIM without having to insert a SIM card. It's not embedded."

Through Mi Roaming, a virtual SIM platform, customers in mainland China are able to purchase roaming plans directly through an integrated app and immediately being roaming without needing to swap SIM cards or use a hotspot. In fact, the SIM card slot can be left empty while you travel.

At Mobile World Congress here, I spent some hands-on time with a Xiaomi phone and several other handsets, including a Meizu and Alcatel device, all of which sported virtual SIMs. Using the app portal, I selected roaming options in various countries, chose a data plan, and made a payment.

Telna can create customized service plans and data caps for phone manufacturers. For instance, users of an Alcatel handset might get unlimited data for $1 a day, while owners of a Meizu might have to pick from several tiered plans that cap at 10GB of high-speed data. It gives each OEM a fairly broad degree of flexibility in the type of roaming options they offer customers and to some extent, takes power from the carriers.

It's definitely an interesting technology and we're likely going to see more companies take note of the advantages offered by virtual SIMs and simplified roaming options.