Post-it notes are one of those archaic products that still manage to stick around, literally, in our offices and homes. With this hack, you can transform the beloved Post-it into a very 21st century digital note system. To leave a note, all you need to do is write it out with your finger on the trackpad. The message will show up on the LCD, which can be erased with a push of a button. It's not the easiest hack in the world, but for only $175 it is not the most expensive either. Plus, with a nice enclosure, it could be very functional. [PopSci]