Motorola has announced a free open hardware platform for smartphones called "Project Ara." The goal is to create a modular smartphone that would allow users to swap hardware components at will. Motorola says it wants to "do for hardware what the Android platform has done for software: create a vibrant third-party developer ecosystem, lower the barriers to entry, increase the pace of innovation, and substantially compress development timelines."

Project Ara consists of an "endoskeleton" case and various hardware modules. Similar to a desktop computer case, the endoskeleton would provide slots for different modules. According to Motorola, "a module can be anything, from a new application processor to a new display or keyboard, an extra battery, a pulse oximeter—or something not yet thought of!" Pictures show a case with spots for rectangular inserts. Each slot has metal contacts that connect the insert to the rest of the phone.

Motorola is teaming up with Phonebloks, a company with a similar idea, to make this a reality. Motorola is letting enthusiasts sign up to be "Ara Scout." Scouts are interested members of the community who can give feedback and share ideas about the design. The most active members will get free devices when Project Ara launches, which Motorola says should be about a year from now.

When Google bought Motorola a year and a half ago, everyone wondered what the search giant would do with a hardware company. It looks like its big plan has been revealed. If the idea takes off, modular cell phones could change the industry. Motorola has a lot of work to do first, though.