I'd post this in /r/Privacy but you all are the homies, not to mention this is a somewhat specific kind of OpSec question.
Without being too self-incriminating, say someone had an android burner phone and wanted to communicate securely with like-minded individuals over SMS... most options out there (Signal, etc.) require the use of mobile data or WiFi, both of which can either be an expensive hassle or a serious security flaw. Most burner phones are not data-plan friendly and data use would quickly drain one's minutes, while open (or cracked) WiFi connections not tied to one's identity are few and far between but cellular connections are ubiquitous.
Is there an app that can facilitate end-to-end encryption over the SMS infrastructure? I know you could just PGP encrypt (or another encryption scheme) your messages before sending, but this requires that both parties have an understanding of how to use PGP and, let's face it, your average stoner with a smart phone doesn't want to go through that hassle. It's hard enough to get somebody to not talk about a product brazenly in clear-text. Signal is great for it's simplicity and compatibility, but the data requirements make it unreasonable for some.
Anyone have experience with something like what I'm talking about or any ideas for where to start looking? The standard google search and a good hour or two of digging wasn't any help. Thanks all.
https://smssecure.org/
Text Secure/Signal used to do that but dropped it so someone forked it out into a separate app.