These are two scripts that enable you to remote control a PC using Dropbox:

Server PC

First run this script on the pc you want to control.

Client PC

Then run this script to pass commands to the server PC.

If you use Windows, then you can run this using Cygwin

Keep in mind that anyone with access to the input file can run anything on your machine! The server script will run forever, so if you wish to kill it, you will need to issue a break (Ctrl+C on most machines) or if running in the background, run

killall -9

Also remember that this script will run under whatever user you are logged in as, so if you do not want it to run with root permissions, do not use sudo/su, or be logged in as root!