Florian Meier explains how to set-up a remote 7″ touchscreen for Raspberry Pi:
There is already a large number of touchscreen solutions for the Raspberry Pi. I present yet another one. The special feature of this solution is that you just need a single HDMI cable to connect the touchscreen to the Raspberry Pi. There is no need for an additional USB cable or any proprietary solution for transmitting the touch information. Therefore, with a long HDMI cable it is easy to place the touchscreen and the Raspberry Pi at different places (e.g. at the wall and inside a cupboard).