The geo API seems rather... specific. Is there really a demand for it?
My problem with many existing geo implementations is they assume that a circular radius is the query type I care about, and longitude and latitude is sufficient to know where I actually am in terms of jurisdiction, etc.
Being able to add fine grained polygons to represent national, state, county or town boundaries and being able to identify the relationships between my co-ordinates and those entities is still far more complex than I would like.
Adding polygon support might be an interesting exercise, actually.
UPDATE: found it https://github.com/RedisLabs/geo.lua
Really? Wouldn't most GIS implement something like OGC Simple Features? AFAIK all SQL GIS implementations follow that (to various levels of completeness, but even MySQL has shapes support since 5.6)
Solution was to add a hidden column for each administrative category (e.g. for US: region, state, county, zcta) to each point record to replace spatial searches with filtering.
Would something like that work for you? What kind of numbers of points and polygons are you looking at and how quickly do you need to solve the problem?
On my wish list would be adding a bounding box query to return results within a map displayed on the current screen: e.g.: https://www.algolia.com/doc/javascript#search__inside-boundi... or e.g.: http://postgis.refractions.net/docs/ST_MakeEnvelope.html