One of the most exciting areas of Internet applications these days are applications that are "mobile native". That doesn't just mean mobile first. It means mobile native – the app could not exist if the mobile smartphone didn't exist.
A great example of this is the "book a cab ride on your phone" category. The leader in this category is Uber which does a great job and really nailed the experience. I've also used SideCar in San Francisco and Hailo in London. All three are great experiences.
These services work so well because the cab driver and the passenger both have mobile phones that are geolocated. The application matches up driver and passenger in real time and handles payment as well. That's a killer experience.
When thinking about new mobile app categories, we like to think about these mobile native services. They are very powerful.