What should I build next?

Hey everyone! Just finished up and launched a project yesterday, now that it's on the back burner for updates and beta testing, I'm looking forward to starting something new.

I have a few ideas of sites or apps that I've collected over the last couple months and figured why not ask WIPer's for their opinion. So, here we go!

  1. A price watcher/notification app for Steam games. Get notified if a game drops below $X or X% off.

  2. SAAS app to help creative agencies keep track of their retainer projects and hours.

  3. A product stock watcher/notification site for e-commerce stores. You'd put in the URL of a product and get notified when a product goes in/out of stock.

Why something new? Why not double down on what you've already built and spend some time marketing it?