"I want to patent a smartphone app."
In many cases, we often cannot give a very good answer. It is very difficult to obtain a patent for trendy technologies for the following reasons.
If you want to get a strong patent and monopolize the market, you need to anticipate trends beyond (or even beyond) the current trends in technology. By the way, it is said that the prototype of the iPad was already completed in 2002. It was eight years before it was released.