It should be possible to overwrite lat/long via the Tracking API. I suggest two new parameters:
Add test cases to test these api parameter with a geoip module enabled.
Also, please suggest Tracking API Reference doc text for new parameters
(In [7480]) Fixes #3481, added extra tracking query parameters: lat, long, city, region, country.
reopening, as the documentation update is needed, can you edit the page: http://piwik.org/docs/tracking-api/reference/ to add doc for these new parameter?
(In [7569]) refs #3481 Phpdoc update
Matt, I just updated the tracking docs, let me know what you think of my changes.