How to use: http://tedgustaf.com/blog/2014/10/google-maps-custom-editor-for-episerver-75/
Source code: https://github.com/tedgustaf/episerver-google-maps-editor
Available on the EPiServer NuGet feed: http://nuget.episerver.com/feed/packages.svc/
Note: Compatible with custom properties used by OpenWaves.EPiServer.GeoProperties. Just change OpenWave's custom property type to string, and the zoom level contained within that string will be eventually migrated over by this addon.