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One possibility is concocting something using "for". It's been popular for years to name products "xyz For Windows", and I don't recall Microsoft attempting to stop this or if they did having any luck in doing so.
Other words, such as "with" might work as well. These might work well for mash-ups involving some Google service. I'm sure you can think up some more joining words that make it clear that your site is some adjunct for use with Google, but does not imply that it is Google itself.