This is the One.
This is the free harmonica app you were looking for. Yeah, its got the cheesy "play with mouth" thing, but its got a little toggle on the other side of the screen (easy thumb reach) for both pitch-bend and blow/draw. so you can ACTUALLY play a harmonica (ish). Hard to get single-hole stuff down, but great for basic wailing.
AllYourBassAreBelongToUs about
Honey Harmonica