It monitors for new drives and looks for a user defined file on the new drive. It then launches another (or the same) user defined app (or batch file). http://www.shrum.net/code/launcher
You can set the monitor file and the launch file. I personally use the same filename.
Example: on each of your external devices, place a batch file named mybatch.bat (or whatever filename you want) on the root of your drive. This will be the batch file that you want your system to launch as soon as the drive is seen. Launcher will see the new drive, see the filename it is monitoring for and launch it. Easy-peasy.
App was written with AutoitScript and code is available...all for free (although I ask of a small donation if you like the app to help with my hosting costs)
Lots of other apps I've written like this at http://code.shrum.net