I have been developing a library to interact with the “REST” API:

https://github.com/academe/sugarrestapi

The documentation needs a tidy-up, and bits need completing, but it works and is in operation on a number of sites. I kind of do a bit more on it for each project. With this library you basically log in, which gives you a login session key. You can retain this session key between pages or users to avoid logging in for every page load.

Once logged in, there are objects for dealing with Entries and EntryLists. The EntryLists support paging, and can pull in data from relationships. Hopefully it will be useful to someone, but please ask if it dos not make sense or you cannot see how to achieve a particular task. Anything that helps me decide what to put into the documentation can only help :-)

— Jason