Growth investors are often on the hunt for the next "monster" stock that can generate multi-bagger returns. These types of stocks are often lesser-known small cap plays with limited analyst attention and institutional ownership.

Therefore, investors who want to catch a monster stock should strike when it's still off the radar. Let's take a look at two stocks that might fit that description -- Energous (NASDAQ:WATT) and Limelight Networks (NASDAQ:LLNW).

Energous

Energous develops a long-range wireless charging technology called WattUp, which charges compatible devices with stationary pads from up to 15 feet away. In theory, this next-gen technology could eliminate the mess of wires behind computers, entertainment systems, and other electronics.

WattUp wireless charging concept.

Source: Energous.

The FCC approved a miniature version of WattUp for Internet of Things (IoT) devices last year, and the company secured manufacturing deals with bigger companies like Dialog Semiconductor. Energous and Dialog produced a small wireless charging RF circuit at the beginning of 2017, which some industry watchers think will be used in the iPhone 8.

However, some analysts believe that Energous didn't secure the Apple deal, and bears have flatly questioned WattUp's ability to charge larger devices "through the air." Others claim that the FCC won't approve the tech for larger devices due to safety concerns.

Nearly all of Energous' projected revenue this year ($10.4 million) comes from its partnership with Dialog, and estimates for nearly 450% sales growth next year depend heavily on its partners shipping marketable products, securing new deals, and obtaining FCC approval for other charging technologies. Therefore, Energous remains a highly speculative play -- but its upside potential could be explosive if its tech actually works.

Limelight Networks

Limelight Networks provides global content delivery network (CDN) services which enable its customers to deliver digital content -- like videos, software updates, and online games -- to any device worldwide. The company has provided those services to huge customers like Microsoft, Comcast, and Disney, but its market cap remains under $400 million.

A graphical depiction of a CDN.

Source: Getty.

Rising demand for CDN services and the end of a patent dispute with its bigger rival Akamai Technologies' (NASDAQ:AKAM) lifted Limelight's revenue annually for the past three quarters. Analysts expect that momentum to continue with 8% growth this year. Its non-GAAP earnings are expected to rise five-fold from $0.01 per share last year (its first annual profit) to $0.05 next year, and another 50% next year.

Limelight scaled up with numerous acquisitions over the years, and Akamai's recent shift away from the CDN market should continue boosting its top and bottom line growth. Limelight's stock has already quietly doubled over the past 12 months -- and that momentum could continue as demand for high-speed CDN services rises with the surging demands of digital content.

Staying under the radar...

Energous is only followed by four analysts, and only 39% of its shares are held by institutional investors. Limelight is covered by five analysts, and institutional investors own 68% of its shares. Therefore, there's still time to buy these stocks before mainstream investors pile in.

However, investors should mind the risks. Energous has rallied about 20% over the past 12 months, but it trades at a whopping 166 times sales and its future growth remains extremely speculative. If Qualcomm or Broadcom -- which are both developing wireless charging tech -- beats Energous to the market, the stock's downside potential is nearly unlimited.

Limelight has a reasonable P/S ratio of 2, but its growth could be derailed if bigger players like Akamai turn toward the CDN market again. Therefore, neither Energous nor Limelight should be considered dependable core investments. But they're still interesting speculative plays which could bust out of their small cap shells over the next few years.

Teresa Kersten is an employee of LinkedIn and is a member of The Motley Fool's board of directors. LinkedIn is owned by Microsoft. Leo Sun owns shares of Qualcomm and Walt Disney. The Motley Fool owns shares of and recommends Walt Disney. The Motley Fool owns shares of Qualcomm. The Motley Fool recommends Broadcom Ltd. The Motley Fool has a disclosure policy.