Original and useful app or something for fun using machine learning?

Long story short, internship fell through so I need something to keep myself busy other than my mind-numbing job and to pad my resume since I graduate next spring.

I have two ideas two ideas for projects, but I'm not sure which to go with. One is an app that hasn't been done before and would be useful to many people, the other is to setup something using deep learning that would be more just for my own enjoyment.

Both will require me to do some independent studying, and I probably won't have time to do both this summer.

There are a ton more entry level jobs doing app development than anything related to deep learning, and the app has the potential to make me a little income. I'm not kidding myself here though- I know the main perk from either of these will be the leg up in job applications, I'm not about to get rich from an android app I wrote over the summer.

While machine learning is unlikely to directly relate to any job I get right out of school, it is more interesting for me. I also will be able put it on my github page so employers can actually see the code. I worry that I might not have a neat point where I can say "this is finished" like I would with the app.

If you were me, which would you focus on?