Anyone heard of this? It's the sort of training announcers do to perfect their pronunciation. You can get an idea of it here： http://www.kurashimamaho.com/vocalization.html

I was a guinea pig for my friend's pronunciation research for her course, and more than anything it's given me awareness. I've made pleasing improvements with typical problem areas like ん, らりるれろ, 長母音, モーラ rhythm etc, but perfecting い and え is going to take time while I develop the muscles in my cheeks.

Before doing these lessons, I'd done a fair amount of shadowing, and I've never had any problems being understood, but I think passively repeating can only get you so far without some level of awareness if you want to lose as much accent as possible.

Pronunciation doesn't seem to get a whole lot of attention since it's "easy", so I wonder what others are doing to sound 日本人っぽい rather than 上手(ですね). Is it worth dedicating any time to 発声練習? Or are there other methods besides shadowing?

I think this may be good practice but listening is the key to pronunciation. (In my opinion.)

In an "advanced" college course, everyone had distinct "foreigner accents". My rhythm and pronunciation isn't native but it's not 外人的. (if that makes any sense) The ironic thing is that I skipped the first two levels of the class and studied by myself while they took all three levels. I practiced Japanese used by Japanese and thus aquired "some" pronunciation habbits.

So in short, I think one just needs to listen to a lot of Japanese and be actively conscious of ones mistake when speaking.

Correction by a native speaker is vital. Without that, I don't think most people will be able to get the best pronunciation they can, so the original idea sounds good.