how it could possibly be useful

1 create a GPU friendly cryptocurrency where the payload includes a two dimensional data set (or image) that is processed with a standardized neural network model

2 let programmers pay a mining fee to expedite execution

3 instead of GPUs doing nothing but redundant calculations and getting replaced by ASICs, mining GPUs can dual purpose mine and execute arbitrary code

Will it be efficient, probably not. It does kill two birds with one stone