Is anyone aware of a tool that allows you to track when Google comes to your site and index it? I know that I can see what the last indexed date was, but I want to see a track record of the frequency of Google coming to my site

You can use server side scripting to write your own processing function, just look at each request's user agent, not all requests will have one but Google will be nice and always provide one. So, look at the request ($_SERVER variables in PHP) and check to see if the user agent is Google and if it is, record it.

Currently Google's user agent string is: Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)