Hand held vocal coach from Roland

The pocket-sized VT-12 is a traveling vocal coaching device. With a variety of built-in exercises and warm-ups and pitch analysis as you sing. The illuminated pitch meter displays your pitch and can even detect two singers simultaneously for two-part harmony.  It also has backing tracks and etudes from the Berklee Press book bundled with it.
http://www.rolandus.com/products/details/1250/525

roland vocal trainer

.