Many investors have wondered when Chinese smartphone giant Xiaomi, the world's most valuable start-up with a $46 billion valuation, will go public. But back in March, Xiaomi's global VP Hugo Barra told Reuters that the company had "no need to raise more money" and no plans to file an IPO.

Xiaomi's Mi 5. Image source: Xiaomi.

Barra also noted that Xiaomi, which generated $12.5 billion in sales last year, is "self-funded" and the funds it raised during six funding rounds have been "allocated to investments." The company has already invested in over 50 start-ups to expand its ecosystem and diversify its business away from smartphones.

But if Xiaomi eventually goes public, its initial investors will likely profit, and the start-ups it invested in will be thrust into the spotlight. Let's get better acquainted with those companies.

Meet Xiaomi's top investors

11 companies and investment firms have invested in Xiaomi. That list includes Morningside Group, Qiming Venture Partners, and IDG Capital Partners -- which are all private firms that are off-limits to mainstream investors.

But it also includes Qualcomm (QCOM -2.72%) Ventures, the investment arm of the world's biggest mobile chip maker. Qualcomm's stake in Xiaomi is unknown, but the Series B funding round it participated in raised $90 million and included five other investors. That round, completed in late 2011, valued Xiaomi at just $1 billion.

Qualcomm's investment in Xiaomi has proven useful before. Xiaomi's flagship devices have always been powered by Qualcomm's Snapdragon SoCs. Xiaomi also quickly inked a new 3G/4G licensing agreement with Qualcomm after the chipmaker claimed that Chinese OEMs were underreporting shipments to pay lower licensing fees. But that investment doesn't ensure long-term loyalty -- Xiaomi recently developed its own first-party chip for its lower-end devices to cut costs and put cheaper chips from MediaTek in its low-end devices in India. Both moves could cause Qualcomm to lose market share.

Meet Xiaomi's top investments

Xiaomi's investment portfolio includes a broad range of companies focusing on mobile games, payments, videos, and online-to-offline (O2O) initiatives. Notable investments in that category include a stake in Chinese game maker Kingsoft, an investment in Andon's connected fitness device maker iHealth, a stake in Baidu-owned video site iQiyi, and a partnership with Uber. Xiaomi had hoped that revenue from those services would hit $1 billion last year, but it only reached $564 million.

Xiaomi owns a major stake in camera maker Yi Technology, which created the action cameras that it sells online in China. Yi's cameras are frequently compared to GoPro's (GPRO -2.57%), because they offer nearly identical hardware specs at much lower prices. Xiaomi also invested in wearables maker Misfit, which was acquired by Fossil for $260 million last year. That investment complements its Mi Bands, which offer similar features as Fitbit's (FIT) low-end trackers for a fraction of the price.

Yi's Action Camera (L) and Xiaomi's Mi Band (R). Image source: Company websites.

Xiaomi signed a mobile payments partnership with chipmaker NXP (NXPI -2.46%) earlier this year, which puts NXP's NFC (near field communication) chips into its flagship Mi 5 phones for payment and transportation purposes across China. It also bought about 1,500 patents from Microsoft in June, which could finally give it the IP muscle to launch its smartphones in new markets like the U.S. and Europe.

Fewer investors, more investments ahead

It could be tough for Xiaomi to generate excitement for an IPO after its annual sales growth slowed from 135% in 2014 to just 5% in 2015. Smartphone sales in China are slowing down, and rivals like Huawei are successfully copying Xiaomi's core strategy of selling low-margin devices online with minimal advertising.

As its core smartphone market gets saturated, Xiaomi will likely boost its investments in other companies to diversify its business. U.S. investors should watch these moves carefully, since they could cause international headwinds for companies like Fitbit and GoPro, and also give it the momentum to challenge smartphone giants like Apple and Samsung in additional overseas markets.