It all sounds great fun and worth blogging or tweeting.
Do any of you practice in a similar way?
No, and never did except perhaps as an angsty teenager. However, I do make it a habit to engage with my surroundings, mentally note textures, smells, people, and try to understand what I am seeing which is the same kind of thing.
Do you think it's helpful? I'd like to know your opinion.
It depends on what you're doing it for, and what kind literary thing you're practicing for.
As a way of engaging with your surroundings, it sounds great.
As a way of practicing for writing prose... less so if you're a genre writer like me. My kind of prose is anchored in the POV character's mentality. So how I experience a crowded bus is different from how my Viking berserker would and thus my choice of words and imagery is different.
If prose fiction
is your bag, then you could tune up the exercise by taking on different POVs when you write your vignette. So you saw a cat and a crow this morning. You know what it meant to you. But what would it have meant, say, to pagan shaman?