FORTUNE — Fitbit, maker of a wearable device that measures health and physical activity, has raised $43 million in new venture capital funding. Fortune has learned that Softbank Capital led the round, and was joined by existing shareholders like Foundry Group and True Ventures.

[UPDATE: The company has now confirmed the raise, adding that Qualcomm Ventures and SAP Ventures have come aboard as new investors.]

TechCrunch had reported back in March that Fitbit was looking to raise $30 million at a $300 million valuation. The San Francisco-based company previously raised $23 million.

“The business is growing really fast,” explains Steve Murray, a SoftBank Capital partner and new Fitbit board member. “It’s a device which means that it really requires a good deal of working capital, unlike all these software apps venture capitalists are usually funding.” He adds that it falls somewhere between software and medical device investing.

FitBit’s new capital infusion also comes just months before Apple AAPL is rumored to be unveiling its iWatch, which may have activity tracking capabilities.

“It would be reckless to say that we’re not concerned at all about what Apple is doing, but it reminds me a bit of 10 or 15 years ago when people would say ‘Well, Microsoft MSFT could do that,’ about virtually every startup,” Murray adds. “And then people said the same things five years ago about Google GOOG . And plenty of young companies have become successful without being destroyed by Microsoft or Google.”

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