In project EV3dev Projects I've found out that the EV3 brick is too slow to handle full fledged REST API. This project was an attempt to create a simpler version of the same idea but more optimized for the EV3. Notable feature also is that it has an GUI for simulation mode - you can watch the simulated robot move around the map.
Project got abandoned before it was fully finished as my goals shifted to other projects, but lot of interesting parts still got implemented.