In DefHack, my team developed a project called EzPen. It is an integrated web
application that detects the movement of your mobile device and utilizes it as a mouse(pen) drawing on laptop.
I built up a webpage to POST phone's acceleration data, and Unity GET the results, caluate the path of the movement, and draw the line on the laptop. The hardest part in this porject is to reduce the errors and latency.