Canonical have announced "Ubuntu for Phones", a version of Linux for smart phones. This is not the first attempt at a Linux based smart phone operating system. There was Openmoko Linux, designed to run on the Openmoko open access hardware design for a smart phone, as implemented in the Neo 1973. I tried Openmoko on the Neo 1973 in 2007, when it was still under development.
Ubuntu is not entirely free of commercial considerations and so might have more success than Openmoko, which petered out in 2009.
Also of interest and perhaps even less proprietary (with less chance of success), is Firefox OS, an open source operating system being developed by Mozilla. The aim with Firefox OS is to use HTML, CSS, and JS for the user interface. That will make it smaller and more portable for phones and tablets, but limit its value as a full version of Linux. Perhaps Mozilla would be better off producing an environment within Firefox which would allow "Apps" to run unaltered on desktop, laptop, tablets and smart phones.