I've already heard about Ranktracker and it was a great surprise for me that it's now here on Appsumo.

I really like this app. And what I loooove the most is the fully mobile compatibility; I can do everything from my smartphone and the UI is really great.
I can see all needed data (I have two small online stores) in one place.

One thing is missing in my opinion. I'd love to see something like Morningscore has: missions to complete to achieve some results. As I'm not an SEO expert it would facilitate my on-site work.

Oh, and one more thing. I really don't understand all these people complaining about low KW limits. If you have 100 customers, I think you can afford to pay monthly billing, right? ;)