There are many tools to automatically check your rankings in many search engines, but people are wary of using them because Google has stated that it does not like automated ranking checkers and at one point a few years ago punished some sites that they identified using automated ranking checkers.
The other search engines seem to be less hostile, but there is one solution that seems to fit your requirements while not going against Googles desires, and that is the new version 3.5 of Webposition Gold, which has an option to use the Google API to check your Google rankings. You buy the software, create an account at Google by following the signup process at the following URL:
http://www.google.com/apis. Google will email your Web API license key, usually within the hour. You enter the API license key into WebPosition and from then on WPG use the Google API to check Google rankings and for which Google allows up to 1000 searches per day.
You may notice some slight differences between the Rankings from the API database and those you get in a browser, but they are usually small.