Since Holiday by MooresCloud is in very short supply (only two exist in the whole world), we've written a simulator to help speed your way into programming great apps for it.
Simpype provides all the pieces needed to run an HTML5, browser-based simulator.
When it starts up, it launches a web server (using the wonderful CherryPy) that listens at 0.0.0.0:8888 (which means it listens to all ports, from localhost, to whatever external interfaces may be attached).
At the same time, simpype instances a named pipe (FIFO) at ~/pipelights.fifo. This is the pipe that any process can use to talk to the simulator. In the general case, IoTAS will use that FIFO when it renders something to a simulated Holiday -- but any program can use it.
We'll document the data format for the simulator another time -- peek at the code, it's not hard.
Invoke as: python simpype.py
simpype will run in the foreground. To exit, send the process a Control-C.
Good luck!