Comfort and safety of new cars in old cars

Hello! I always like to read the advertising brochures of the cars that come out new. At fairs you will be bombarded with them and I always take some with me! Most of the time the nice frills have made to the cars, which you could perhaps also build on some older cars. I don’t mean now: “Today I build myself an active steering” or something, that is of course not feasible but other things I find quite interesting! For example this comfort flasher of the Sharans (not quite new anymore) or the new A3 has, for example, the function that the rear wiper affects when the windscreen wiper is activated at the front and you insert the reverse gear. I think this is also quite easy to replicate with 1-2 ICs. And my electrical knowledge is really not the best! And what interests me especially is a nice function, which has among other things the new 406. That’s when the warning flashing system turns on automatically when you are on the car and as soon as you release the brake completely or give out gas again. So you can leave both hands on the steering wheel, if you have to e.g. drive towards an unexpected stowage end and dodge. My question therefore: How does this actually work? For example, you can think of other nice details that you could build up?