Ask HN: Worthy ideas? Critique my thought process

Let me say that I truly enjoy all the wonderful comments you've made to this community and it's been a great source of inspiration for me.

tldr; #1 Can't find a really good finance related idea to build upon

tldr; #2 Not sure which platform to target

I'm interested in building something on my own but I have some questions that I thought I would run by HN. I'm interested in business and finance but I can't seem to find an idea that I feel compelled to spend countless hours on. I have an idea or two and usually when I begin, I sometimes finish but the hardest part is finding someone who will purchase it. I have built some apps and while there could be feature improvements, I don't think I have been hardworking in adding those features.

I've been flopping between platforms (web, iPhone, Android, Windows) with no focus. It's probably bad and I feel that I should focus on a single platform.

I reckon PG's advice on how ideas aren't worth anything and how you execute is all that matters is probably true in this case.

Thanks!