The consensus seems to be twofold. The hardware side of things is too cumbersome -- there's no pins broken out anywhere. And the software environment doesn't help either.
We're spoiled for scripting languages (with hardware support libraries!) on the Raspberry Pi. Not so on cellphones.
I wrote an Ask Hackaday column because I find this a horrible waste. And there were some great approaches suggested in the comments -- this project is basically a lit review.