I've used Response Tap to track conversions from Google search advertising campaigns. The calls have improved our conversion attribution, giving us more credit for the ads we serve for our clients.
Our client has a two-step conversion process, with conversions that come in needing to be vetted/qualified. Response Tap's 'user history' attribute is instrumental in this as it displays the user's clicks IDs which then gets uploaded back into the ad platforms, letting us include the 'confirmed' conversions in Google Analytics and our automated reporting. Review collected by and hosted on G2.com.