Unfortunately for a mobile ssh client it doesn't appear to be available for any mobile OSes (yet). I would be delighted to see a nacl version of this turn up for chrome. An android client is on the horizon.
I don't have a chromebook but on my chromeos I can press ctrl-alt<F1> to get to a command line. From this I can use the normal ssh. To get back I can press ctrl-altF7. Using this I can use several different TTY to get a couple different ssh connections going. You could also install screen on the remote host so that the session stays live even if the connect drops.