I do not know a word of Chinese, but finally I can add sound to all those ”mute” internet adds… (ˆ_ˆ)
Unless you have a CJK keyboard/typing device it is a bit hard to use, though. I picked random signs from the System's floating Unicode palette (click the flag on your menubar), and discovered that Pinyin Dictionary only covers the mere basics. If you input some sign from the extended sign blocks, like "CJK UNIFIED IDEOGRAPH-20021" (𠀡), the program yields nothing.
I guess actual readers and learners of Chinese script will give this app their thumbs up. Let's wait and see…
(A final wish: Why not include IPA transscription as well? That would be a perfect way to learn Mandarin. [I assume the program gives the Mandarin pronunciation of the signs, though it does not explicitly says so - which it definitely should!])