I work for a music software company and we are thinking of developing a product that fretless and double bassist (as well as violinists, cello players, any fretless instrument) may find of use. It would basically be a "finger finder" application that tells you when you were fingering correctly and your intonation was on or off. It would be used with a PC or MAC with a Mic or a using the audio in for the computer. It would also track progress (i.e. if you are practicing the C major scale, it would show you where you were hitting the notes and where they should be, giving you a score). Do you think this would be a useful application? What other features might be helpful?