So here's an immediate and simple technique that can give you a very vague idea of the same thing. (And I do stress it's very vague!) It just involves looking at the search engine results page for a particular search. And it works best for keyword phrases with 2 or more keywords.
Basically, if all the keywords appear repeatedly in all the titles of the results down the first page and the next and so on, then webmasters are clearly targeting it. It stands to reason that you'll probably find it very hard to get one page one. Take a search like "make money blogging". You'll see all those three keywords appear in almost all the listings for several pages.
But if you try a search like "make cash blogging" then those three words don't appear in the titles as consistently. Sure, they appear a lot, but not next to each other so often. They're more broken up. So people haven't targeted this search so much. (And it makes perfect sense that they wouldn't, since the search volume is much lower than the one above.)
Of course this is a bit like comparing apples and oranges, because similar keyword phrases have different search volumes. And I doubt it would hold true all the time, since there are so many factors in SEO. Still, it does tell you something of value pretty much straightaway. That is, it can give you an idea of which keyword phrases you should probably avoid if you want to rank for them quickly and easily.