How to programmatically get Google results without problems?

I've wondered for awhile how I can use software to make searches through Google to check serps to see if a page is indexed, etc. I know some commercial sites like SERP checkers are doing this to some extent, but does anyone know if there is a Google api or a proper way to be able to search in some limited fashion even if the api has usage fees attached?

I realize it's possible to a very limited extent to directly query before Google flags the IP but with how big Google is and how much it ties into, there must be a way to do it.

Thanks

You need to use Google search valid proxies, other way captchas will start appearing