I have recently dug into Pronterface code and realized that there is simple RPC server built-in. It listens on localhost and it's really cool feature for remote monitoring, so I hacked KISS (Keep It Simple and Stupid) PHP code that allows querying the RPC server through the web. The code can query multiple running Pronterfaces and it's no problem to monitor multiple 3D printers which are connected to the same host. Running instances of Pronterface are automatically detected. It also queries all connected V4L compatible webcameras, which means that you can check progress of printers visually. With the current code you can check temperatures (bed, extruder), Z position, status of the current print task including task/file name, ETA, finished percentage.
The code with instructions is available from github: https://github.com/yarda/printrun-webmon/. Feel free to pull request patches.