Lawnchair is an interesting library for persisting data on client side. There are multiple adapters, each specifying a new way to store data locally on client.
For example PhoneGap-SQLite lets you store data in a limitless SQLite database through PhoneGap bridge.
It stores new key-value pair for each record. Spine's default local storage implementation stores the whole collection in a key-value pair.
Inspired by Spine's Ajax adapter and existing similiar project.