Blynk appears to be a fairly put-together library for not only hooking up any Arduino or esp8266 to a phone through WiFi, but also through the net if desired. Install the app onto your iPhone or ...

You usually think of using Blynk with an Arduino, but you can also program the embedded part directly on an ESP8266. I quickly threw together a little prototype joystick.

Android/iOS: If you want to control a Raspberry Pi or Arduino connected device from your phone, you’d usually need to know at least some programming.