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.