I am planning on coding an app no matter what, but I'm wondering if this will help in college admissions. I don't have any organized extracurriculars in programming, and since I'm indicating it as one of my interests on my app, I think I probably should. This project will take up a lot of my time (60-100 hours at least), and if it won't help for admissions I'll wait till i'm done with my applications and then do it. If it helps for admissions then I'll find the time to do it earlier.
For the record, I'm considering very competitive colleges including Stanford, MIT, CalTech, Harvard, Princeton, and CMU CS school (plus safety and match schools of course). Is this app project something that could tip the scales for me? I have very high test scores and grades, so I'm not worried about meeting the baseline academic qualifications.
I think it's a great idea to code an app to showcase your passion and skill in programming to colleges. This is something that will make you stand out in a pool of exceptional applicants, especially if you plan on studying computer science. A project like this shows drive, ambition, and enthusiasm for your area of academic interest.
That being said, you also need to make sure you can afford to spend this much time programming while keeping up with other schoolwork and college applications. If you think your grades will slip if you really throw yourself into this, I'd say to take it slow and not worry too much about finishing before the application deadline. If you're not finished, you can still mention it in your application and include the name of the app so that colleges have the ability to see the final product when it's complete.