I wrote custom software using Meteor.js to trigger Midi events with touchscreen devices (2 iPads, 5 iPhones and 1 android phone). All these devices connect to my laptop over WiFi and trigger a different set of midi notes. Combining this with the Performance Mode in FL-Studio allowed me to pull off this performance.
This isn't an app. It's a custom built web application running locally, that sends midi events to my laptop. But people are gonna comment to ask: "What is the app called that he uses?". So for people reading this description, let's respond to them saying that the app is called: MidiWifi Launcher v3.2