Having built a ranktracker before, and still being good friends with people who run one of the biggest rank trackers on the market, using the google API's simply isn't an option.

Simply put, the API never returned the results in the exact same order as the actual search results did.

The best / most reliable rank trackers did (and still do) simply use proxies to get around the google captchas. I've scraped millions of pages from google over the years, and with enough proxies, the correct proxy delays/timeouts, and other little tricks you pick up along the way; you can actually scrape google pretty easily.

This is especially true with the dropping cost of proxies. I'm obviously an exception considering I run several scraping SaaS and have generally specialized in it for years, but I can he hitting x.com with 30,000 different IP's within the hour.