I am having trouble finding a NoSQL databases that officially support MonoTouch via a local DB on the device. If their are, could someone provide a list of them here.
A bit late, but still relevant:
I'm the author of MarcelloDB, and I just released version 0.3.0 on nuget.
MarcelloDB is a document DB, built specifically for mobile apps (light-weight, low memory usage) and supports Xamarin Android and iOS as well as the windows platform.
I still have some features I want to add before reaching v1, but the file format and existing api are allready quite stable.