I did a similar thing earlier last year mining litecoin on a few dozen computers in my school's lab. What I did differently was I had a script running finger every few seconds which killed the miner if someone else was logged on to be nice to other users/avoid detection. I ended up making about $5 over a few days before stopping it out of guilt. In retrospect it was a really stupid thing to do; too much risk for too little gain.
One suggestion would be to use timeouts to add a delay to the input event handler, so it would wait until the typing has stopped for a while rather than recompiling on every key press. That's just a line or two of extra js and should make the auto updating vastly more usable.
