I think I had one working on my Touch using python.. can't seem to find anything about it now. I regularly use other clients on my phone and PC and found the Kindle one too slow and cumbersome to be worth the hassle so I deleted it.
Also, after you fetch the feeds, you need to read them, obviously. This requires a browser (not an easy way to call the builtin one) or an external browser, or conversion to .mobi or something. Many hoops to jump through.
on a side note, have you tried
http://webtoread.com/
they have one subscription every day free.
Good luck in your searching.