Just thought I'd post that we have a database SDK which now works on the iPhone. It's called Raima RDM Embedded, and it supports both the network and relational database models, replication and access using SQL or a native API. The replication could be used to send data to a remote device natively right from the database, without having to rely on anything external like a web service.

This product has been around awhile and is in use in many embedded systems, but this is the first time it's been on the iPhone.

We made a free app as a working example of the SDK, which just got released on the AppStore, called AirportSearch.

We have information, and a free download on our website- http://www.raima.com/products/rdm-embedded/sdk-download/

Hope this might be useful to some of you!