got to love it when a iphone app is named, and the referenced, with no consideration that the same name may be used for something else in the open source world (namely a webkit based browser, that one can actually run on the nokia tablets).
anyways, i have heard of such services, tho never tested it. sonyericsson have included it in their phones for a while i think, and there are also webpages where one can upload recordings and get a return, iirc...
not sure if they can pull of a good match from a hum or some singing tho...