This much I know about Amazon Kindle, if you are in the wrong niche you are barking up the wrong tree. It really is that simple. You can get a few sales here and there, but if you want to be truly successful on Amazon Kindle then you need to target the right niche market. I get all that.

My question is, this is a hassle to do manually using Kindle's auto suggest system, are there any tools preferably free that you use to find hot niches on Kindle?

Here's the second part of my question. You may be able to find rough ideas regarding a hot niche, but is there another tool or a set of tools that you can use to cross-reference potential demand?

Again, if there are any free tools, mention that first. But I'm serious enough about Kindle publishing that–yes, I am willing to spend money on an online tool. It just has to be very good.