I voted for this app as I think it is a really worthwhile development. However, I think the real niche for this would be on a PDA.
Minimusic have had this in RnD for ages. I don’t know if the hardware would support it, but I can’t think why not.
For me it would be almost a pinnacle for mobile music making. To be able to get a device to pick a hummed or whistled tune on the fly and then drag it in to another piece of software to manipulate or develop it. Cool.