Sony Corp. (6758) has opened the insides of its SmartWatch in an effort to lure developers and drive innovation before the potential releases of similar devices by Apple Inc. and Samsung Electronics Co. (005930)

Sony is sharing technical details to allow developers to write their own firmware, or code that is embedded into the hardware of the watch, the company said on its website Friday. The timepiece already accepts user-created apps.

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“We hope to see even more innovation,” the Tokyo-based company said on its website. Included in the materials on Sony’s website is a “SmartWatch hacker guide.”

The move comes amid expectation for surging sales of watches that perform similar tasks to smartphones as Apple (AAPL) and Samsung chase Sony to develop their wearable devices. About 1.2 million of these digital watches will be sold this year, generating $370 million in sales, according to an estimate from ABI Research. Sales may jump more than 20-fold by 2015, the research firm forecast in May.

Sony introduced the SmartWatch last year and expects sales to grow as the company and other developers add to its library of more than 200 applications, it said in May.

The SmartWatch wirelessly connects to smartphones running Google Inc.’s Android software with Bluetooth technology and alerts users to calls. It also connects to Facebook Inc. and Twitter Inc. and controls a wearer’s phone-based music library.

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Samsung said in March it was developing a wristwatch similar to a smartphone, and people familiar with Apple’s plans said in February the company has about 100 product designers working on a wristwatch-like device.