[skidooer]

Not key/value, but Mobile CouchBase (CouchDB) supports iOS and apps using it have been approved for the App Store.

An interesting point to note is that Mobile CouchBase is primarily written in Erlang, so porting any existing key/value stores is not dependant on their native language being C or C++.

[stephth]

True. I haven't tried it and it looks promising, but currently it depends on packages like Erlang, Spidermonkey, and OpenSSL, so adding Mobile CouchBase to an app means increasing its size by about 42MB.