Metronome

I don't want this to get off topic, but I did want to mention that I think it's really silly when teachers force their students to NEVER look at their hands. There are some passages where it is necessary to watch different things... On the other hand, in some places (the octave jumps in the right hand near the end of Liszt's Mephisto Waltz, the octave jumps in the left hand in the coda of Chopin's 3rd Scherzo, the last chords of Chopin's 2nd scherzo, etc) where it's good to practice without relying on seeing. When I have to do this, I go to a practice room at my local college (one with no windows ) and turn the lights off... it works well!

But anyway... back on topic