It looks like they don't offer M2M plans, and their cheapest plan appears to be ~$20/month(I guess? I don't see a recurring billing option). Maybe it's the cheapest if you are sending 500+MB of data per month but it seems hologram(or some other M2M sim provider) would be cheaper.
https://communityphone.org/
These guys can beat their prices. and are YC alum.