Human interfaces, sure, but there's a good chunk of industrial sensing IoT that might do some non-trivial edge processing to decide if firing up the radio is even worth it. I can see this being useful there. Potentially also in smart watches with low power LCD/epaper displays, where the processor starts to become more visible in power charts.

Wonder if it could also be a coprocessor, if the fabric has a limited cell count? Do your dsp work on the optimised chip and hand off the the expensive radio softdevice when your codesize is known to be large.