The USB Vision and Posture Reminder keeps you sitting straight and holding proper distance to your computer monitor.

This USB gadget would drive me mad. The device chimes and flashes when you are too close to the screen.
I have a slouching problem. I am actually slouching right now while writing this. I would need another device that reminds me, when I start moving away to far from the screen. I know enough people though, that have their eyes so close to the screen that you would think they are counting the pixels.
The Homi USB Posture Gadget sells for $27.00 on USBGeeks.