Ubuntu Linux (and Canonical Ltd) has the same approach as Maru OS. I guess Ubuntu Convergence has been in public longer period of time than Maru OS. The downside compared with Maru OS is you can't make phone calls while using your phone as a PC. That, I think, is not that bad as I hate phone calls which break working day.
Ok, there is one more player in the market. Microsoft already has their Continuum out there. If you are interested, follow the link and read more. The basic idea is the same as with Maru OS and Ubuntu Convergence.
My (Ubuntu Convergence) tests resulted today a TV screen filled with Ubuntu Desktop. I'm pleased since this I didn't know when woke up. In life you never know what comes across. So, what happened?
- I had installed Ubuntu Touch alongside Android using MultiROM and TWRP on my Nexus 4 many times before. This time install channel ubuntu-touch/rc-proposed/ubuntu was chosen as it is the right one for the purpose of Convergence... as far as I know, not 100 % sure though.
- With help from Sturmfluts blog I managed to attach and boot HDMI-cable, Slimport adapter and Nexus 4 the right way in my TV (the only full HD monitor I have!).
- And voilà! Suddenly Ubuntu Touch appeared on TV. The position of Desktop on TV is far from perfect, but that doesn't matter. Fine tuned later! (The idea is to offer a genuine Ubuntu with windowed apps on bigger screen).
What is going to happen next? Well, a bluetooth keyboard and mouse are needed. Those I don't own. After that some tuning so that the whole Unity Desktop can be seen. And that's it! If I make it to the end I can start to use my Nexus 4 as a Desktop Linux PC! Meanwhile, take a look at LibreOffice Running on an Ubuntu Phone (The Verge).