The toolbar offers a number of features that make web browsing easier and more informative. Check out Google for more details.
The toolbar is being used by someone browsing your site. That's why you're seeing the user's IP Address and not Google's IP Address.
As for why it's hitting your home page so often, perhaps someone is using Firefox with the auto-reload extension installed and has the refresh rate set to five minutes. I do that with several of my own websites all morning and evening except I use three minutes.
If it's a major annoyance there are ways of dealing with it. Let us know if that's the case please.