For the prototype Whare Hauora gateware units, we're using Wemos D1 Minis, with a shield. These are cheap to print because they have such a small surface area (printers charge by the area).
It's got space for a 2.4GHz transceiver and a sd card. (yes that's the same frequency as the wifi, but in our tests they are fast and share the spectrum time nicely enough).
