There is a project on Github called diyHue. This is actually a pretty good working Hue emulator.
Copied from their repo:
This project emulates a Philips Hue Bridge that is able to control ZigBee lights (using Raspbee module or original Hue Bridge or IKEA Tradfri Gateway), Mi-Light bulbs (using MiLight Hub), Neopixel strips (WS2812B and SK6812) and any cheep ESP8266 based bulb from market by replacing firmware with custom one. Is written in python and will run on all small boxes like RaspberryPi. There are provided sketches for Hue Dimmer Switch, Hue Tap Switch and Hue Motion Sensor. Lights are two-way synchronized so any change made from original Philips/Tradfri sensors and switches will be applied also to bridge emulator.
I 've tried to create a hass.io addon for this however I noticed I’m way to unexperienced for this. Maybe someone else could give it a try.
Yep, that’s because HA does the work the Hue app would do. Can understand this project if you want to control other systems with the Hue app as a sort of poor man’s HA but if you need a Pi to run this on you might as well do it properly with HA.
HA’s light controlls are complicated and the gui is ugly if i want to have HA in my house i need a simpel gui so my family can controll the lights and they know how to use the hue app.
To complement Max’s work I have created a diyhue integration which will connect diyhue to Home Assistant and expose your Home Assistant lights in diyhue and then on to the hue app - check it out here: https://github.com/diyhue/diyHue/pull/523