Why does your personal statement have to be 'sub-par'? Just because you don't have insane extra-curriculars doesn't mean your PS can't be good. If I remember correctly, you're going to be talking about academic interests for the the majority of your PS anyway. Do some reading on computing related stuff that interests you and try to make your passion for the subject show, the app you created is definitely something solid you can talk about as well. Get your teachers and the people at the TSR PS review forums to go over it until you're sure it's the best it can be.