serverless postgresql

For ease of configuration and other reasons, I would like for my
single-user GUI app to be able to use postgresql in-process as a library
accessing a database created in the users home directory. I think I
could possibly get what I want by launching a captive copy of postmaster
with appropriate args but it seems conceptually cleaner to not have a
seperate process at all. Has anyone tried to do anything like this?

I've looked at sqlite and it might be workable for my project but I
would prefer the more standard and featureful SQL of postgres. In
particular sqlite lacks date arithmetic and has some funny type issues
(it claims to be typeless, except when it isn't, or something).