What tools for developing mobile applications are currently relevant?

Question

Android

It is planned to develop an application (a client for a web service, mainly working with api, the application has only an interface) for ios and android. The application will be quite large, but no very unusual things are planned, most likely, it will be possible to get by with the native tools of both systems.
Are there any means that allow making an application for these two systems at once with minimal cost? Or would development of standalone applications be a better option?