Apple Inc. plans to bring satellite connections to its smartwatch in 2025 and is ramping up work on a blood-pressure feature, seeking to entice hikers and health-conscience consumers into upgrading their devices.

The satellite capability is slated to come to next year’s Apple Watch Ultra, the company’s top-of-the-line model, according to people familiar with the matter. The technology will let smartwatch users send off-the-grid text messages via Globalstar Inc.’s fleet of satellites when they don’t have a cellular or Wi-Fi connection.