NoSQL for mobile apps?

I don't think there's an established NoSQL backend for native mobile apps, but Couchbase Mobile is a great NoSQL database with implementations for both iOS and Android.

iOS: http://www.couchbase.com/products-and-services/mobile-couchbase

Android: https://github.com/couchbase/couchbase-lite-android

I wouldn't be surprised if there's a Tokyo Cabinet port for mobile OSs; but seriously, what would NoSQL bring over the SQLite library already included in every platform?

• simple semantics. it's just as easy to do key/value in SQL as it's on any NoSQL database
• scalability. a multipetabyte-capable phone doesn't qualify as a mobile platform.
• trivial sharding. clusters of phones aren't so popular yet
• small implementation. tokyo cabinet source code is 4.8MB, SQLite is 4.7MB. no real gain (and it's already there).

in short, you can just use SQLite as a 'small NoSQL' if you want. it's quite fast too.