It basically started when I read that the deep back muscles cannot be trained by voluntary tensing but only by unconsciously during keeping balance. This appears to be oversimplisitic but it led me to the idea of one leg balancing in everyday situations. After starting to use it in a few limited situations (preparing fruit basket) I added more and more situations and now use it automatically in most situations that involve standing like washing, preparing meals, waiting for commute etc. It doesn't cost you any time adds some minor fun to many of these tasks and as far as I can see has reduced my back problems.

Beside the balancing I started to add some more gymnastic-like motions to my program when I started fencing. E.g. when (un)loading the dish-washer I do quat-like or lounge step motions. When lifting things I focus on avoiding to bend over but instead use the 'correct' weight lifting motions. And I take the fencing stance or parts thereof as often as I can.

I can't remember where I read about this. Could have been this source (German) or this one. After quite some searching I turned up these English links: Wikipedia on the relevant muscles with some exercises and this physiotherapy article with many details. The latter explicitly mentions unstable balancing as one exercise in a complex therapy setup.