The app actually listens to the notes you're singing or playing, and figures out in real-time if you're hitting the correct pitch. It's implemented as a very simple game, where you score one point for each note you hit correctly.
I've taken a radically different approach to the development of tunologist. Whereas I would usually "crunch" for a few weeks, working late at night or early in the morning for a few hours a day, tunologist was the project I started working on just after my daughter was born. It was actually an experiment to see if I could still work on a side-project in addition to helping to look after my daughter, and working a day job. It turns out I can!
I wrote tunologist in increments of less than 30 minutes per day - I would guess my median was actually about ten minutes. Before doing the project I never would have thought it possible to do good work under that kind of constraint. But it's not so bad as you might think. It forces you to spend a disproportionate amount of time thinking, and planning your next move, for example while commuting.
I've spent a little over 130 days on this project (about 22 hours total, assuming an average of 10 minutes of work per day). I'm happy with the result, and I think it's time to let other people play with it.
If you're interested in the development process, I blogged the whole thing at http://prehacked.com. My first post was http://prehacked.com/28852894 (I wish posterous had a way to put "next post" buttons on individual posts, so that it would be easy to read the whole thing in order).
Please let me know what you think (and feel free to post your high scores!).