As I'm sitting and working with a laptop I have to remind myself to straighten my back often. Again and again I find myself in a bent or sloppy posture which is not very healthy when you spend a lot of time on a chair near a desk. It's easy to forget when you don't see yourself from aside.
A chair could be made that would simply inform you to straighten up when it would detect (using sensors or cameras) that you have deviated from a healthy posture. A person could choose how annoying the chair is - if you wanted to learn fast, it could scream at you every time you've taken a wrong position. If not, it could use more gentle alarms, harmonious sounds, shine or blink in colorful light, etc.
The user should be able to turn the reminders off completely whenever they wish. The chair could also have an intermittent relax mode - to let you get loose and sit however you feel like from time to time to let the back muscles rest for some time and then bring you back to a healthy posture again.
It could be coupled with the app on your desktop and a window in the corner of the screen would always feed back to you how your posture currently looks. A figure in a correct posture would be shown in parallel and as you straightened up you'd have to match that figure in a little game manner until you saw an affirmation that it is correct now.
There are products based on the same concept, but they are mostly wearables like this
meant to be attached to your back and vibrate whenever you slouch. While a wearable has an advantage that you can use it no matter if you sit, stand, or walk, the main disadvantage I see is that it might feel uncomfortable to always have a device sitting on your back. An item that you use anyway like a chair or a backpack is different in that regard.
A chair would only correct your posture while sitting, but its big size lets it have all kinds of cool features built into it, so the concept of a smart chair can be expanded beyond just something that straightens your back. It could have speakers to play music and feel the baseline while sitting on it, light up in various colours and intensities to serve as a night light, etc. That kind of chair would be a cool piece of furniture to have. What else could a smart chair do?