Sure, I'll check it out. I plan to rework the current POI search to use the concept of POI providers, so that more POI search services can be easily used (currently modRana uses just Google local search). Okapi could be implemented as one of those providers, at least initially.

BTW, I think you'll have to add quite a lot of stuff to support Geocaching correctly. Stuff like arrow to cache, multi stage caches, reading/leaving comments, those weird calculators, sorting by cache type, etc. But yeah, just showing the caches on the map should be a good start.