[rcheu]

I use http://intonia.com/index.shtml for this purpose. It's available on Android/iOS as well.

It's not free, but I think the functionality is a bit better than this. It handles fast passages and can change temperament, show how off you were, etc.

[ctrager]

I've tried it. It's all the good things that you say, but it's kinda hard to use/read. I was aiming at something that would be easy, immediate, fun.