[[[ To any NSA and FBI agents reading my email: please consider ]]] [[[ whether defending the US Constitution against all enemies, ]]] [[[ foreign or domestic, requires you to follow Snowden's example. ]]]
(I changed the subject from FLOSS to FLS, because free (libre) software is the way I want to describe this field.)
I see two freedom concerns, in the project description.
1. The tablet.
I think all tablets are sold with a nonfree operating system, but maybe some tablet can run Replicant (the free version of Android).
I presume your software runs on Android. Is the entire app free software? Specifically, does it avoid nonfree libraries, including the Google Play Servics library?
2. The Raspberry Pi.
The Raspberry Pi is an unfortunate choice because it can't run _at all_ without some nonfree software.
If what you need is a single board computer, how about recommending one of the models that can at least start up without nonfree software?
See fsf.org/resources/hw/single-board-computers for information.