Developers looking to get their hands on the first smartphones running Mozilla’s Firefox OS had to move fast: GeeksPhone, a Spanish manufacturer that sells phones directly to consumers, sold out of both the Keon and the Peak within just a few hours after their launch Tuesday, citing “great demand” for the devices. GeeksPhone said it sold roughly 1,000 of the devices and promised to make more available Wednesday morning.

This week’s debut of Firefox OS handsets is not a major event, of course. GeeksPhone isn’t exactly Best Buy, after all, and both the Keon and the Peak are targeted directly at developers rather than consumers. But there are some other important reasons to keep a close eye on Mozilla’s mobile operating system as it comes to market this year.

The price is right, and so is the timing

Perhaps the most compelling aspect of Firefox OS is the low price of the supporting devices. The Linux-based OS is programmed entirely in HTML5, JavaScript and other web technologies, which should help manufacturers produce smartphones that are more affordable than those running more traditional technologies. Indeed, the Peak sells for about $195, and the Keon for $120 – unsubsidized prices that mark the very low end of the smartphone market. Meanwhile, Telefonica O2 hopes to introduce a Firefox OS smartphone in Brazil for less than $100.

And affordable handsets are crucial for tapping the emerging markets Mozilla will initially target. Firefox OS will roll out to Brazil, Colombia, Hungary, Mexico, Poland, Serbia, Spain and Venezuela over the next several months before hitting Asia and North America. Growth in many of those markets will be explosive for the next several years, as Analysys Mason recently pointed out. Meanwhile, carriers around the world are increasingly looking to low-end smartphones as they try to squeeze more money out of users who have traditionally carry feature phones. Which is why low-end smartphones may account for nearly half of overall smartphone shipments by 2018, as ABI Research predicted this week.

Operators around the world are rushing to support Firefox OS, seeing the platform as a way to retake some control of the mobile market from Apple and Google. Mozilla has assembled an impressive list of 18 carrier partners including America Movil, China Unicom, Deutsche Telekom, KDDI, Sprint and Telefonica. Manufacturing partners include Alcatel, Huawei, LG and ZTE.

An intriguing player in a very crowded field

And while GeeksPhone’s sellout is sheer anecdotal evidence, there certainly is a lot for developers to like about Firefox OS. Its reliance on familiar, open web standards without proprietary extensions makes it easier to code for than Android, iOS, Windows Phone or BlackBerrry OS. Firefox OS allows developers to tap even the most basic phone functions – including dialing, SMS and camera features – to be tapped through HTML5 apps. And Mozilla is building a JavaScript API that will make it easier for app publishers and content owners to accept money from Firefox OS users either through credit cards or carrier billing deals.

Firefox clearly faces huge challenges as it joins a cutthroat market that seems to get more crowded by the day. HTML5 is very much a work in progress and simply can’t touch native apps when it comes to delivering a rich, immersive user experience. The technology’s lack of support for DRM may scare off content owners fearful of piracy or illicit sharing. Most daunting is the fact that emerging markets have become a white-hot battleground where Android’s dominance will be challenged by Windows Phone, BlackBerry OS and upstarts like Samsung’s Tizen and Ubuntu (which may actually be a more polished platform than Android OS). But Mozilla has formed an impressive alliance behind its mobile operating system, and its strategy of initially targeting emerging markets with affordable – if somewhat rudimentary — smartphones is a wise one. Developers, OS providers and just about everyone else in the industry should be paying very close attention.