I actually just got one of these FeatherWing boards. I was thinking about using it with the nRF52 Bluefruit LE - nRF52832. Seemed like a cool way to add a UX for interacting with the bluetooth stuff.
Cool! That could be useful if you need a complete handheld UI. There are already an ILI9341 and STMP811 drivers. I suppose it will need a custom keyboard driver over I2C. There is also a GPIO expander, Neopixel, microSD. I don't know which GPIO expander is on the board. GPIO expanders are a nuisance because you can't get off the ground without first having the GPIO exander. The LCD backlight, touchscreen, microSD and keyboard all depend on the GPIO expander. Not for people who need immediate gratification.
I had originally though to use this with the Giant Board that Adam has been working with. I am having motivational problems, however, and getting things shipped to Costa Rica is slow and/or expensive.
