A good place to get ideas on phone apps is in social forums that target mobile users and developers. Many ideas as well as complaints are found in these forums. The complaints from users are great in terms of feedback as they will tell you what not to do with your app. Developers will also tell you what you should avoid when creating your app due to design complexity and programming tool restrictions. Most of these forums are free and you only need to register to participate in them.
Knowing how to make an app has never been more vital. Apps are everything. Without them, a PC is a typewriter, and a smartphone or tablet is a slab of glass and metal. If you've been bitten by the app bug and hanker to make your own, getting started can be intimidating. This feature points you at tutorials, explainers, resources, and videos that can help you learn how to make an app.
We're not forcing you towards Apple's maw either - although we do cover how to create apps for iOS and macOS, there are also lists for Android and Windows, along with a cross-platform list covering concepts and ideas every app can benefit from, and technologies that can be deployed across a range of platforms. In some cases you'll gain knowledge, but some tutorials even leave you with a complete (if simple) app to mess around with.
The only restrictions on your part are the kit required to work on the tutorials (which may be as little as a device to watch videos, and a whirring brain to take everything in), and time. Money isn't generally an issue, because all of these tutorials are freely available - or at least freely accessible using trials.
This little book will give you the basics of making and selling Apps.