I think that for embedded platforms such as phones, Raspberry Pi’s, other microcontrollers etc. it is probably more worthwhile to use ETS (Erlang Term Storage), as it is built-in in the language, and therefore a lot faster to communicate with it. ETS was also built from the get-go with concurrency in mind, and can also be used to create RAM-based memory stores, which makes it a lot faster (of course, at the cost of using more RAM)
On the other hand, ETS takes some getting used to, because it does not use a conventional Structured Query Language syntax, but rather a pattern-match esque syntax.
And while I do not know how good (or bad) SQLite will work with concurrent applications, I do know that it really helps to have the same database locally as on a production server. In the past, we’ve had rounding troubles with our decimals when going to the test and production environments, because SQLite doesn’t care about the precision of DECIMALs, while MySQL and PostgreSQL will. And the same is true for STRING vs TEXT, which is the same in SQLite, which means that MySQL might throw errors in production when suddenly things don’t fit in something you thought could be a string.
