Do you know phidgets? That are little USB devices which I support with my plugins. There are phidgets with sensors like distance, reflection, weight, touch, motion, voltage, temperature and a few more. There are several motors available, RFID readers, displays, LEDs and couple more.
I personally have a Text LCD Display here for testing.
So if you want to write an application which emails the user if the temperature in the server room is too high, you can use the temperature sensor.
And believe me, there is a lot of money you can make if you offer consulting for companies in your area to help on automating operations. For example how about an app which uses a sound and a light sensor to detect people, activates a camera and sends an email with the picture to some security personal? Maybe also using a RFID sensor on some key locations where a security guard can identify itself and being not a burglar?