Investors looking to buy shares of companies that make devices have plenty to choose from. Apple (NASDAQ:AAPL) and GoPro (NASDAQ:GPRO), however, are especially promising. Both firms derive the overwhelming majority of their revenue from the devices they sell to consumers.

Photo: Apple

Apple's devices make it the most profitable company in the world
When it comes to companies that depend on the sale of devices, Apple is by far the most successful. Indeed, it remains the largest and most profitable company in the world. Today, Apple's business largely depends on three devices: the iPhone, iPad, and Mac. The business profile of each one is different, but all show promise and are contributing to Apple's bottom line.

In terms of the iPhone, Apple's last two quarterly reports were historic. From the beginning of October through the end of March, Apple sold a total of 135.7 million iPhones, the best two-quarter period for the iPhone in its eight-year history. In Apple's fiscal year first quarter, the iPhone's average selling price surged to $687, a new all-time high, and remained high ($659) in the second quarter. The iPhone 6 has been a global hit, as Apple's share of the smartphone market increased in nearly every region following the iPhone 6's debut. It's possible that the iPhone could eventually lose steam in the quarters to come, but for the time being, there's nothing to suggest that the iPhone business should slow down.

When it comes to the iPad, the story is a bit different. Unfortunately for Apple shareholders, that business has been in decline for over a year. iPad sales have slipped and under-performed analyst expectations in recent quarters as the tablet market in general has shown unexpected weakness. Still, it's a business that generated more than $5 billion last quarter, and as Apple pushes into the enterprise space, it could see some level of resurgence. Meanwhile, the Mac continues to plod along steadily. It's not a massive business for Apple (only slightly bigger than the iPad) but it's outperformed the broader PC industry. Apple's Mac sales rose 10% annually last quarter, defying a 7% decline in the broader PC market.

Over time, Apple's business could shift, with new products rising in importance as older ones decline. This includes, notably, the Apple Watch, as well as the Apple TV. Yet Apple is still likely to remain a device maker, as its integrated hardware-software strategy is the fundamental essence of its business model.

GoPro continues to grow rapidly
GoPro is much less proven than Apple -- its business model remains somewhat speculative. Still, GoPro's growth has been tremendous, and it may have more upside than any other device maker that's currently trading. GoPro posted revenue growth of 54% last quarter as demand for its flagship action cameras remains strong. Unlike some other recent tech IPOs, it's a profitable company -- its operating income surged 135%, and its net income rose nearly 150%.

GoPro faces plenty of competition, but, perhaps because of its brand recognition, it continues to win sales. According to IDC, GoPro accounts for about 57% of the global action camera market, while its closest competitors have only single-digit market share.

In time, it's possible that GoPro's products could become commoditized, but it's taking steps to ensure that it can continue to succeed. On GoPro's last earnings call, the company's President, Tony Bates, drew attention to the investments it's making in software. GoPro has an editing suite, GoPro Studio, that allows owners of cameras to easily edit the videos they've recorded. Although GoPro Studio can work with other cameras, many of its features require the use of GoPro's own HERO devices. Demand for this software has been rising rapidly -- downloads rose 138% last quarter. Once video has been edited, users can take it to the GoPro Channel, a network of videos taken and uploaded by GoPro users. GoPro is making use of the growing number of Internet set-top boxes and video game consoles to popularize this content, and its app has been installed on 1 million Xbox video game consoles.

For now, GoPro remains tied to its action cameras, but in the future, it could offer a more diversified device portfolio. GoPro intends to enter the consumer drone market next year. It's too early to tell if GoPro will find success, but there's clearly a demand for consumer drones. The current market leader, DJI, expects to generate over $1 billion in sales this year -- a little more than half of what analysts are expecting from GoPro's action cameras alone this year.

GoPro has given early shareholders a rough ride, as the stock has been immensely volatile since its public debut. Still, if it can continue its tremendous growth, it could reward shareholders in the long-run.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.