Hi all,
I've just finished writing an App that lets you see and hear music rhythm notation on your iPhone or iPod Touch.
Great for checking the rhythm of a tricky section of some sheet music or score, simply tap in the notes/rests/ties/triplets set a time signature and BPM and it'll play the rhythm along with a metronome.
There's more information
and screen shots here
If anyone uses it and has feature requests then don't hesitate to let me know, I'm a very responsive developer!