Just throwing this angle out there ... it depends on a few factors.

Let's say you've got a blog for a local business that really has little momentum. The fact that they are getting any links that is from an external IP address (given that is the case) may be better than if they hosted that same content at domain.com/blog.

To me though, if it is done right, and the blog is getting traction, visits, shares, retweets, and links, you would prefer those are associated with your main domain, i.e. domain.com/blog

I'm not a fan of the subdomain option, assuming it shares the IP of your main domain. That is kind of the worst of both worlds.

I have come across a cool site called https://www.appannie.com/ that gives you some analytics, but nothing like search volumes, or even better, ability to track rankings within Google Play Store or iTunes app store. Still new, but really hoping somebody does something like this.