Validating your idea by Google Search Terms?

Was wondering if any of you do this/how accurate of a metric is it? Using those keyword/term search tools that shows interest in some particular thing/niche i.e. searches per month. I had a specific app I had to make for a friend recently and I was wondering if I could scale it up so random people could use it/pay for it.

I was going to search and see if people were looking for that specific tool by Googling for names/words tied to the app.