Smartwatch pioneer Pebble is launching a programme for third-party developers to make sensor-equipped straps for its latest devices.

It has released a series of 3D printer files that will allow the designers to create prototype "smart straps" that feed data to its forthcoming Pebble Time watches, expanding their range of functions.

Pebble's chief executive Eric Migicovsky said smart straps had the potential to make his products the best fitness trackers in the world by adding heart rate monitors, GPS location chips, extra batteries and other sensors as they became available, as well as unleashing other possibilities.

The Silicon Valley-based start-up's move has been praised by the tech press.

"It's a brilliant idea because it allows a small company like Pebble to stay relevant for longer without having to invest a lot of money to keep up with everyone else," commented Stuart Miles, founder of the Pocket-lint gadget site.

Pebble Time - which features a colour e-paper display - has already attracted over $12m (£7.8m) in pledges from more than 54,500 backers on the crowdfunding site Kickstarter.

Pebble unveiled a premium steel edition of the timepiece at the Mobile World Congress trade fair to help attract fresh interest.

The BBC's technology correspondent Rory Cellan-Jones met with Mr Migicovsky in Barcelona, and asked if he feared Apple's entry into the smartwatch market in April.