What apps don't exist yet that you would like to use right now?

Do you ever wish there was such an app? What kind of app is it? The world is already overflowing with many apps. However, there must be some nice apps that you want. If there were such an app, I would want it right now! What is the app that you think "If there was such an app, I would want it right now! Please tell us! This time, we will limit ourselves to Mac apps, iOS apps, and Android apps.