I'm not sure of immediate applications. But imagine a situation where you have robots using biopolymers [1]; such storage could be part of their long term storage (along the lines of Amazon glacier).

I could also envision a more complex scenario where specialised cells with data encoded into DNA are injected into our bodies, and these cells use recipes / content encoded into DNA to create compounds and biomolecules needed under specific circumstances. The drug glands in Iain Bank's culture series comes to mind, though I'm sure there are other examples in sci-fi.

Also, long term, self replicating, error correcting slow storage. Your storage will be a cell culture plate, or cells frozen in liquid nitrogen. Just DNA polymerase has error rates of 10e-8 / base pair, which decreases to 10e-10 inside a cell with repair / error correcting enzymes.

I'd think that's good enough if the DNA isn't copied too many times. Besides, if you have a population of cells with the same DNA, the probability of the same error across all cells (which are independently replicating) ought to be very low, even accounting for AT/CG biases, repeat sequence / poly-nucleotide runs, etc.

Exciting stuff.

[1] Get ready for robots made with human flesh - https://arstechnica.com/science/2017/03/get-ready-for-robots...

This article talks about using robots to synthesise tissue grafts. But you could also imagine robots with biological membranes / circulatory systems..

(Edit: added paragraph describing possible 'organic storage')

Organic based file storage would give a whole other meaning to the phrase, "my disk died."